It felt like finally teaching my son to hunt. But instead of wilderness, our game preserve was the industrial zones northwest of downtown Denver. And instead of the ducks my grandpa used to shoot in Minnesota, our quarry was freight trains.

I had hopped freight trains a lot, from this city, my hometown, thirty-some years before. Old-time tramps camped along the creek had schooled me: Don’t catch on the fly if you can help it. Just walk into the yard, figure out which train is which, and climb on before it leaves. It’s a lot easier. And safer, I came to learn, than trying to board a moving train.

But Asa, an 18-year-old New Yorker, appeared to have grown up on the same movies I had—the ones where the hero hops a rolling freight and steals a ride out of town, the law in hot pursuit. He’d been disappointed when we got to Denver and I explained that my goal, actually, was to avoid that scenario. Instead, as I sketched it out in the Starbucks that is part of the REI store that has since been built about 200 yards from where those hoboes camped back in the eighties, we would stalk a train at rest. We would sneak up on it, find a vulnerable spot, and hide ourselves there before it moved, thereby avoiding the loss of our legs.

“Seriously?” asked Asa.

I was out-of-date when it came to Denver: yards had shifted, railroads had new names, bicyclists pedaled where tramps had trudged. But savvy freight hoppers had acquired a new weapon during my years away: an underground book by an anonymous author that offered dense detail on how and where to catch a train out of seemingly any freight yard in the continental United States. Photocopied pages were passed around; I’d gotten several from a Montana-based rider I knew. Asa and I now looked at the pages in the Starbucks, comparing locations with the map on my smartphone. By following the bike path alongside the South Platte River just outside, we could walk all the way to the Burlington Northern Santa Fe (BNSF) yard and, unless the situation had changed, sneak in through a hole in the fence. I guessed it would take 45 minutes.

I picked the grainer, pointed it out to Asa, began my sprint alongside the train as it neared, and grabbed hold of the ladder when it drew even with me. I was on. Seconds later, Asa was aboard beside me. There is no thrill quite like it.

“OK, but look at this,” Asa said. He had noticed that our route, according to the guide, would lead right by “a great place on public park property to wait for the trackage rights train (if you want to catch on the fly).” The spot featured a pair of park benches. “Your train will be leaving from across the river, going L-to-R and will make a sharp U-turn to the R over the river.”

“It’s on the way,” he observed.

I agreed to check it out with him. And as we shouldered our packs and hit the path, a warm July breeze washed over us and the spirit caught me: this was like a treasure hunt. We had the secret map and were headed for X. I had a feeling I was about to give in.

We arrived at the appointed spot and reconnoitered. The benches were close to the U-turn, but the track there was out in the open, visible to all the world. We walked alongside it on a small bridge over the river, past KEEP OUT and NO TRESPASSING signs, and into a zone of white storage tanks. Beyond the shade of a highway overpass were fences that marked the edge of the railroad yards; bangings and rumblings issued from within.

“The train will come from there,” I said, pointing. “We’ll have to run alongside it here.” I paused to identify a section of track. “See how loose these stones are? Think you can run on those?” I knew he could. Asa nodded. “OK, then. Let’s wait.” We retreated not to the benches but to the shade under the railroad bridge, which was closer to our catch-out spot.

It took only about an hour. We heard the deep bass vibrations and variable whine before we saw the engines, appearing just where the guide said they would. We hustled over, scrambled up the dirt under a railroad bridge, jumped a fence, and beheld our quarry from a few yards away.

First came three deeply reverberating locomotives, with tiny windows and long vented panels hiding their massive diesel engines. Behind these intimidating machines, three times as tall as us, appeared a long chain of gigantic metal boxes that rocked and squealed independently, their faded maroons, off-whites, browns, and blacks tagged with spray paint and stained with rust. If the engines recall the magnificence of America’s westward settlement and industrial power, the mixed freight cars, dented and weather-beaten and covered with graffiti, project an air of dystopian ruin. When you’re just a foot or two away, they make your heart pound.

MY FIRST book grew out of my senior thesis project in college. I wanted to write an ethnography of railroad hoboes and to research it by traveling with them. My advisers liked the idea but noted that riding the rails was illegal. I asked, What if I left college and did it and then came back? Might be OK, they answered, so I did. The book that recounts that experience, Rolling Nowhere, was published about a year and a half later, in 1984. At the time, America had more than a dozen major freight railroads instead of just seven, Reagan was trying to bring down the USSR, trains still had cabooses, and I was single and didn’t have a son.

By 1994, the year my wife, Margot, gave birth to Asa, all that had changed. And something else happened on that day: I began to worry. Mostly I worried in the way that all parents worry, but in addition I began to worry in a way that was fairly singular. I worried about whether and when that seed I had planted, the idea of riding freights, along with several others, might intersect with the curiosity of a growing boy.

Of course, I wanted him to read that first book of mine, as well as the others that followed, about my travels with Mexican migrants, my job as a prison officer, and more. When he was 14 or 15, I gave him copies. But when he didn’t immediately pick up Rolling Nowhere, let’s just say I was fine with that.

Then, early last year, I saw him reading it. Uh-oh. “Great book, Dad,” he said, as I passed his bedroom.

“Yeah? You liked it?”

“Yeah, liked it a lot.”

About a week later came the moment I’d been fearing. We may have been in the car. “You know your book, Dad?”

“Yes?”

“Well, I wanted to ask—if I ever wanted to go on a trip like that, would you teach me what to do?”

“You mean how to ride the rails?” I already knew what he meant.

“Yeah.”

Saying no, we both knew, would be hypocritical. So instead, I offered the compromise that had already been worked out by two sides of myself: the young-man-adventurer and the father-adventurer-who’s-a-little-more- careful-now.

“Well, I would if we could go together.”

He didn’t hesitate. “Sure.”

With the train rumbling past, I told Asa where to stand. Then I jogged away from him toward the back of it and nervously waited for the right kind of car—one we could ride. When one finally drew even with me, I set off at a sprint, trying to keep up—and decided I couldn’t.

“Too fast!” I shouted at Asa, waving him off. My rule: the train couldn’t be going any faster than I could run, and this one, well, possibly was. It was hard to be sure. It had been a while. As we stepped away from the train, I thought ruefully that at 22, I probably would have grabbed it.

Both of us were disappointed. We decided to continue up to the place with the hole in the fence. From a parking lot to the west of the Denver Coliseum, according to my guidebook, just underneath the elevated Interstate 70, one could walk to a small park. “About 150FT SW in park there is hole in fence,” the guide noted. “When built, ready to depart, train will usually be on 4th track over from hole… Train goes to Provo M-W-F and terminates. To Stockton via Sparks/Roseville on T, Th, Sa, Su. Departure time ranges from 2 p.m. to midnight.”

We found the park, nice and grassy and with a mound that afforded a view of the yard and the Rocky Mountains beyond. The hole in the fence, surprisingly, was still there. We didn’t go through it yet, because we didn’t need to: the fourth track was empty. We waited. And waited and waited and waited. We bought cans of beer a couple of blocks away and waited some more. “This is what riding the rails is really like,” I said.

The sun disappeared; clouds had gathered as the hot day grew cooler, a typical summer-afternoon pattern. Rain would follow; would it fall on us?

The answer came about an hour later, at dusk, preceded by gusty winds. Hoping to avoid getting soaked, we passed through the hole in the fence, en route to a protected area under the interstate overpass. I gave my son a lesson in how to cross over a parked freight train. “Step there, not there or there.” It was important not to place your foot where it could get smashed. “Hold on tight to the ladders. Always be ready for a jolt, always be listening for it.” (Jolts could sometimes be heard coming, car by car, as a distant, unseen locomotive either pulled or pushed.) The wind picked up, pelting us with dirt. And then came the rain, wetting us even under the overpass. This, I remembered, is also what riding the rails is like.

Asa and I huddled in the dusk and then saw it—a train moving into position on what looked like Track 4. The only odd thing was that a train worker was riding the unmanned engine at the end, something uncharacteristic of a train about to leave the yard.

We decided to pounce anyway. We jogged down the edge of the yard, hoping we were out of view of the man on the engine, looking for a rideable car. Finally, I spotted one—a covered grain car, basically a long cylinder with the ends beveled in so that grain will empty toward the middle. Under these bevels, at either end, grainers have a small platform upon which two or three riders can sit. I pointed toward one such platform, grabbed the ladder, and hauled myself aboard. Asa followed, swinging himself and his pack up like a natural. We settled in and fist-bumped.

The train trundled on into the main yard, about a quarter-mile away. We pushed ourselves back toward the frame of the car, both to keep a low profile and to stay out of the rain. After about five minutes, we glimpsed high fences and a control tower and areas flooded by lights. Deep in the yard now, the train came to a stop. Stopped trains were on either side of us, too; it was dark and quiet where we sat. On the one hand, this lent a sense of protection and enclosure. But I also knew that a train about to leave the yard is usually on a track that sits apart from the mass of others.

We waited two hours, maybe more. We snacked and spoke in low tones. “If this doesn’t move by midnight,” I said to Asa, “let’s get out of here and get a room at a motel.” Asa said OK. I then boasted, memorably, “Bet you I can toss this banana peel on top of that boxcar.” OK, said Asa, let’s see your throw.

As he told me later, it was too dark for him to actually see the peel when I launched it into the air, my arm reaching through a ladder and constrained by it—I had to use mainly my forearm, not my whole arm. Asa claimed that he heard it bounce off the side of the boxcar and then hit the ground.

This became relevant when, 15 or 20 minutes later, a jiggling headlamp lit the space between our train and the boxcar in question. I peeked out and saw that a brakeman on a four-wheeler was approaching in the narrow, graveled space between the trains. To our surprise and fear, he stopped the vehicle just a couple of feet away from us, got off, and proceeded to shine the light on his hard hat over the coupling by our platform and then over the platform itself. He gasped audibly when the light shined on us.

“No worries, no worries,” I assured him, waving. “We’re just a couple of guys trying to catch a ride out of here.”

“What?! Oh,” he said. Brakemen were occasionally robbed on the job, and I didn’t blame him for being scared. “You guys are going to have to leave,” he declared.

“Sure, sure,” I said. “No problem. Just show us the best way.” He began to walk us out.

“We kind of got stuck in there,” I explained.

“You really scared me,” he replied. He was a young guy, heavy and with shaggy whiskers.

“Sorry about that.”

He explained that the downpour had backed up a lot of train traffic; nothing had been moving for a while. I asked if things would be moving again soon and he answered that yes, he thought they would. We came into view of the gate leading out of the yard. I’d been thinking of ways we might sneak back in until I saw a La Quinta motel just beyond the gate. We were cold and tired, and I had a credit card. “This is not what the hoboes do, needless to say,” I explained to my son, checking us in. But he already knew that.

Why had he stopped right at our car? we asked each other into the night. I had neglected to ask him. Asa, though, felt pretty sure of his explanation: the brakey had seen the banana peel.

You might be wondering, did I have to ask my wife? What kind of mother lets her son ride the rails?

I guess one who has done it herself. Before we met (on a British Rail passenger train, actually), Margot had heard me on the radio, talking about Rolling Nowhere. Though not exactly a thrill seeker, she was always interested in trying new things. Before we were married, I had taken Margot on a freight hop now jokingly referred to in the family as the Train Test. From Salt Lake City, we’d boarded a train to Grand Junction, Colorado, and she had acquitted herself admirably.

In fact, the only things that went wrong on that trip were my fault: running out of food and water hours before it was finished, for example. And the trip had even ended early. When the train stopped a few miles west of Grand Junction at 1:30 a.m., I told her, “Time to get off—we’re there!” But we were not in Grand Junction. We were in Fruita. The sole motel was closed, and we were forced to sleep on a concrete picnic table in the small town’s park, to the music of drunks snoring on the other tables. Margot scarcely complained. This, I said to myself, was the sort of woman you could take some long trips with.

Our train jerked forward, then back. Asa neatly grabbed a bar to steady himself and I looked away. My anxiety over the possibility of him tumbling into the space between our car and the one behind had grown and grown despite my efforts to tamp it down with reason.

My own father was equally amenable to his grandson riding the rails. Though he’d lived a fairly conventional life as a trial lawyer in Denver, he was in favor of adventure. In fact, he had pretty much encouraged me to take my first one, a 1,000-mile bicycle tour of New England with a friend, Lane, who was also 15 years old. We’d had to make the money for it—from mowing lawns—but he’d helped us plan (we had to know which hostel or campground we’d be at every night), and then he accompanied us on a plane to Hartford, where he rented a car and drove us to a country town so that we could start our journey on a quiet road. I still remember assembling our bikes with him in a small parking lot, loading up the panniers, and then, as we pedaled away from him, catching a glimpse of a look on his face that I will never forget, one that said, essentially, What have I done?

Later, Dad and I took a bike tour together down the coast of Oregon. He hadn’t flinched when, in high school, I spent a summer in Pamplona on a home-stay program and ran with the bulls. Nor when I confessed to him the night a friend and I had streaked the high school play (The Music Man). He seemed a bit jealous when a different friend and I decided to get to college on the East Coast by riding our bikes from the West Coast. Later, when I took a year away from school to work for a poverty program in Dallas, it struck him as a good idea, and when I considered transferring from Amherst and wanted to check out a couple of alternative-type colleges, he went with me.

My proposal to leave college again to ride the rails, however, had not been immediately endorsed. Mom and Dad wanted to sit down and talk about it, see if there were ways to minimize the risk. This was before cell phones, so being in touch would be difficult. Could I travel with a friend? they asked. Not really, I said. Ultimately, I suppose, they gave their blessing because they believed in permission. Letting me go dovetailed nicely with Dad’s conviction, which I’ve seen grow over the years as car seats became mandatory and helmets proliferated and parents seemed to become more cautious and protective about everything, that being a good parent means guarding against being too careful.

In July, just before Asa and I set out, my father celebrated his 80th birthday in Colorado. Margot, Asa, our daughter, Nell, 17, and I headed west to join him. Many of his kids and grandkids were thrilled when he offered to sponsor a paragliding outing in the mountains. He led the charge. Later, Asa and I sat with him and talked about our plan. He mentioned to Asa that he himself was my age when I had taken him out to ride the rails. We’d ridden a freight train from Denver over the mountains to Grand Junction, where we slept at the Salvation Army. Then we recrossed the Rockies on a scenic, little-used route to Pueblo, from which we hitchhiked home. So that’s my dad.

Railfanmotels.com, a site that lists “motels & hotels with a railroad view” all across the country, recommended our La Quinta. It even listed the best rooms for trainspotting: 319, 321, 323, 325, 327, 329, 331, 333, 335, 337, 339, and 341. We took 321 and could see the yard’s midsection, where we had been caught.

The next morning, we walked back to our original catch-out spot near the benches. After a couple of hours and the usual false alarms (engines engaged in switching would appear at the end of a string of cars, only to stop and reverse back into the yard), we heard a train that sounded more committed than the others. By this time, we’d scoped out a better place to wait than we’d had before: a patch of riverbank shaded by alder and box elder. To reach the tracks from there meant climbing a fence, but we practiced and found we could get to our staging place in less than a minute. We’d use the same strategy: I’d select the target car and jump on first, to make sure the choice was good. Once I was aboard, Asa—who’d be waiting 50 feet ahead of me—would follow.

Whether this train was moving slower or we were braver, I’m not sure. I picked the grainer, pointed it out to Asa, began my sprint alongside the train as it neared, and grabbed hold of the ladder when it drew even with me. I was on. Seconds later, Asa was aboard beside me.

There is no thrill quite like it.

The train continued on its slow, steady way for another 15 or 20 minutes, then stopped. We were now in Denver’s Union Pacific yard, and there was a lot of road construction nearby. We stood pressed against the grainer’s frame, in the shade, as far out of sight as possible, not talking. Workers passed us on foot, and several black SUVs rolled by; on close inspection, anyone could have seen us and reset our progress to zero. We waited nearly an hour. When finally the train jerked into motion, the sensation was pure relief. As it picked up speed, we moved into the open and exhaled, sitting on our packs in the breeze and taking in the sights of the industrial exurbs.

I remembered the route to the mountains as a circuitous one that looped around farther north than expected, so I patiently awaited our approach. The train, however, never turned west. After we skirted Boulder and reached Longmont, I knew that this was not a train to Grand Junction. We were headed to Cheyenne, Wyoming. I broke the news to Asa.

“That’s OK,” he said. The beautiful mountain passage had been my particular goal more than his. He had just boarded a second time on the fly and was simply enjoying his first ride on a freight train.

Longmont had lots of train crossings, and periodically motorists waved at him. “Is it OK to wave back?” he asked. For sure, I said. At one crossing, three teenage girls on foot caught sudden sight of him; they looked amazed. He waved. Two waved back. He was thrilled. Who wouldn’t be? I had felt the same way.

Berthoud, Loveland, Fort Collins… You can drive from Denver to Cheyenne in about an hour and a half. But, to judge by our progress, we were on course to make the trip in about six hours—freight-train time. Freight trains are noisy, and between the screeching of the steel wheels beneath and in front of us and the booming of the grainer itself, it was hard to talk. Quickly, our hands and clothes got covered with dirt; freight trains are also filthy. But Asa and I shared water and candy, and we reached out to touch the other’s arm to point out sights on our respective sides of the train: cattle feedlots, herons and raptors, antelope. Hidden in the brake equipment around us, Asa spotted an abandoned nest.

Around dusk on the outskirts of Cheyenne, the train stopped again, and I asked Asa where he thought he’d want to go from here. North to Billings, Montana? Or west to Salt Lake City? It made a difference, because westbound trains would leave from a different yard.

Asa asked about the terrain in each direction. Northbound would likely be more of the same, I guessed; westbound would be a bit more mountainous. The western sky, at this moment, was a thousand shades of pink and red. Asa voted for west.

The train stopped yet again on the south side of Cheyenne. And here, for the first time, I appreciated what a profound difference it made to ride a freight train with a smartphone. Google Maps let us see exactly where we were relative to both yards. At the moment, still stopped, we were actually closer to the Union Pacific yard, our next departure point. Also according to Google Maps, we were close to a number of motels. “Best to get off right here,” I said. We gathered up our gear and within a minute were making our way down the side of a steep railroad embankment and into a field not far from a couple of main roads. We put down our bags and sat on a couple of large rocks.

“Can we catch the next train tonight?” Asa asked.

“We could,” I said. “but I don’t think we should. It’s going to be cold, and you’re -going to need another jacket. The next ride could be long, and we don’t have a lot of food left. Here we can eat and sleep. I’m tired and I think we should.”

Asa was disappointed—he was ready to adventure on—but he said OK. We found a room at the Guest Ranch Motel, grabbed dinner, and turned in.

A long walk through town to a catch-out point recommended by my guidebook brought back a memory of a stroll on the same streets with a friend of mine maybe 25 years before. It had been October and cold, and our backpacks attracted the interest of the police, who basically followed us in their cruiser for the better part of the morning and stopped us to check our IDs. Finally, we’d shaken them, but I told Asa about how towns can assume a certain coloration in one’s memory after an experience like that, and Cheyenne had for me. (My friend, now 60 and afflicted with cognitive problems, no longer remembers the visit.)

This time we attracted no heat. The UP yard was unfenced, and we sat on an old piece of carpet at its edge, partially shaded by a scrubby tree. A guy in perhaps his thirties carrying a small pack walked by and paused.

We’d seen a handful of other likely riders in Denver, but this was the first tramp we spoke to. Dressed in clean denim and a work shirt, he was just beginning his trip. He was sick of Cheyenne and going to try his luck in Casper, he said—the BNSF would get him there. Otherwise, fuck it, he’d go to Elko (in Nevada, on the UP). Just be careful on the BNSF north from Cheyenne, he warned—trains pass through Warren Air Force Base, and MPs will arrest you if they see you. My guidebook said the same thing.

After he left, I commented to Asa that my goal in college had been precisely to get to know guys like that, no matter how borderline unhinged they might have seemed, and to travel with them if I could. There had been more tramps back then, I added—by now we would’ve seen several occupied “jungles,” or hobo camps, on the edges of freight yards. As it was, we had seen signs of occupation, such as cardboard that had been slept on and ashes from small cooking fires, but only a handful of travelers. “Are you interested in meeting the people around here?” I asked.

“No,” Asa replied. He’d met his share of dropouts over years of riding the subway, he said. “I’m happy just riding with you.”

And in watching how I broke the law, he added. “Because I know you as a very law-abiding individual. Honestly, when I read your stories, I’m surprised.”

“Really?” I asked. I told him I didn’t think of myself that way—frankly, I was more interested in not getting caught (avoiding the negative thing) than in obeying the law (espousing the positive thing). But on reflection I could see how I’d given him a different impression. “I think it has to do with being a dad,” I told him, at the same time wondering whether it had been so necessary to be that kind of a dad, the scout-leader kind, as opposed to somebody more openly agnostic about rules.

Trains started rolling in. There was plenty of traffic but few places to ride: in the 20 years since my last hop, the rolling stock has changed. Almost all boxcars now have their doors closed and locked. Automobile carriers have doors on the end that prevent one from climbing up and entering the top floor, which the old design allowed. More and more freight trains are intermodal, meaning that their cargo is solely containers, off-loaded directly from ships: the big metal boxes sit on special flatcars, most with nowhere to ride. We watched as two westbound intermodal freights, and one eastbound, stopped in front of us for their crew changes—we the remoras, they the big sharks. Only one of the flatcar configurations, the 48-footer, has a safe spot for riding: a recessed compartment, or well, at one end. The last time I’d been in one, in Spokane around 1990, my companion and I had been discovered by a railroad special agent, who took down the info on our IDs and said he’d arrest us if he saw us again. I didn’t tell Asa that.

Out of view of the tower and the engines, we shouldered our packs and climbed between the trains, looking for a well. Hoisting oneself up and jumping off a train takes agility, and I have less than I once had; also, I was nursing a sore knee. Asa, with the heavier pack, had no trouble at all.

We walked a long way in the narrow canyons between trains, searching but not finding. We returned to the shade of our tree. There, the wait was short. Around 1 p.m., a mixed freight pulled in. Ten minutes later, we were climbing aboard another grainer. And within a half-hour, we were headed west.

The first moments of a freight ride haven’t changed for me at all—they’re still like the beginning of a romance, everything new, exciting, energized. A rush of new inputs: sights, sounds, smells. A brand new start; where will it lead? We tried staying out of sight until we were well out of the yard, out of view of the tower. Then we took some pictures of each other and of ourselves together. And then, outside Cheyenne, the train moving at a good clip, we sat back and made ourselves comfortable for a long ride.

At one crossing, three teenage girls on foot caught sudden sight of Asa; they looked amazed. He waved. Two waved back. He was thrilled. Who wouldn't be? I had felt the same way.

The next crew change would be in Green River. Driving Interstate 80, which was occasionally in sight, it takes about four hours. The train, of course, would take a lot longer. As we passed through the hot afternoon, we watched the grassy plains yield to rolling green hills and then to rockier, red-soil hills with craggy pines. All the while, rain clouds gathered dramatically around us.

Late in the afternoon, the clouds hung heavy and dark. A few beams of light shot through for brief periods, a fabulous light show. But then the holes closed up and the clouds burst. We stuffed our gear into the opening in the grainer’s frame and pressed ourselves in as far as we could go, succeeding in staying mostly dry. “I’m glad we didn’t find a flatcar to ride on,” I said. “We’d be soaked.”

In late afternoon the train, which began the trip robustly, made a prolonged stop in Rawlins—to refuel, we were pretty sure, though we couldn’t really tell, since our part of the long train was well outside the yard. After a while, Asa asked if he could climb on top of our car “like they do in India.”

I told him not to—the first time on the trip that I had said a thing like that. For one, he’d be conspicuous to anybody who was looking. For another, stopped trains, as I’ve mentioned, can start with a jolt at any second, and I didn’t want my son to topple 25 feet to the ground.

The prospect of Asa getting injured had been haunting me the whole trip. And as we moved deeper into that long night, it grew. The view from our perch on the back of the grain car was of the shiny steel wheels of the car right behind us. Our platform had ladders at either corner, a horizontal bar at chest height that spanned its width, and a four- or five-inch lip that wrapped around the floor. That was it—nothing else to stop a fall if the train took a sudden jerk and one of us lost our balance. I didn’t know how I’d be able to live with myself if that should happen.

It was a bit before midnight when the train stopped again, still not having arrived in Green River. We took the opportunity to finish the cheese, fruit, and crackers, and I told Asa the story of how I’d been in Green River before, by mistake. I’d arrived in Salt Lake City on the D&RGW, spent some days with tramps I’d met there, and then decided to continue on my way north or west. I’d hopped on a freight that had rumbled north to Ogden and then, to my surprise and without stopping, turned east. I’d been stuck. Hours and hours it continued in the wrong direction, with me huddled in the rain beneath the axles of a trailer on a flatbed car, in October, until finally the train stopped. Shivering, I gathered my things, dropped stiffly off, and learned from a clerk at an all-night convenience store that I was in Green River. Which I caught the next westbound freight out of.

Asa said he remembered some of that from the book. Our train jerked forward, then back. Asa neatly grabbed a bar to steady himself, and I looked away. My anxiety over the possibility of him tumbling into the space between our car and the one behind had grown and grown despite my efforts to tamp it down with reason. Finally, I told him.

“It may not be logical, Ace, but I’m totally frightened that you’re going to fall off the train.”

“Why? Do you think I’m being careless?”

“No, not at all. In fact, I’m impressed by how quickly you’ve picked everything up. You’ve paid attention to everything I’ve said, and you get how a train works. You’re brave, but you’re not reckless.” This was pretty much my highest compliment.

His mother had tried preparing him for this concern of mine on the night before we began our journey. “He’s probably going to be really nervous,” she said of me to Asa. “He was with me, I know that.” Now I explained how 99 percent of my previous riding had been by myself or with tramps and brought with it scant need to watch out for others.

“So this is a new role for me, because during our lives together, one of my main responsibilities has always been to keep you safe. And this is somewhat dangerous. So it’s hard to shift gears. I’m having kind of a hard time with it.”

Seldom had I spoken so directly to my son about my own difficulties.

After a minute, he placed his head on my upper arm as if resting. Then he put his arm around my shoulder. I put my arm around him, looked straight at the back of the grainer rumbling in front of us in the dark, tried not to cry. Wished the moment would last and last. It was one of the nicest things ever. How much credit can we take when a kid turns out well?

Eventually we pulled into Green River. It looked only vaguely familiar by the light of the yard’s sodium lamps. When the crew had changed and we started rolling again, after half an hour or so, Asa and I laid out our sleeping bags. I knew that about 30 miles west of Green River the tracks forked: there, without stopping, our train would either head northwest, to Pocatello, Idaho, or southwest, to Ogden. My goal was to wake up and use the maps app on my phone to learn our destination—but instead I drifted into an uneasy sleep.

I half-woke at dawn, rousing Asa as the train approached the outskirts of a city: Ogden. When it stopped about a mile from downtown, we got off and walked. Rescue missions are often clustered near the train yards in western towns, and soon we passed one. Its big JESUS SAVES sign had a changeable-letters sign underneath; today’s message read, WE NEED TOILET PAPER. A few blocks away was another shelter, and I told Asa that, back in the day, this is where I would have headed, to wait for breakfast with the down-and-out folk who were currently lined up outside, the doors having not quite opened yet. Asa seemed fine about missing that.

He was so tired that when finally we took a seat at a popular breakfast spot, I had to stop him from putting his head down and falling asleep. It would be better to eat and find a room. I got the waitress to plug in our phones while we waited for pancakes; the phone was key to finding lodging. It helped us discover that the motels within walking distance were all either too nice or too grungy. (Google review of the Budget Inn: “Nasty and full of druggies dont stay there!!!!!!!!”)

Instead we grabbed a bus to Salt Lake City, just an hour away, and fell asleep late morning in a Hampton Inn, where we slept until dusk. Then it was time to discuss what came next.

“Honestly, Dad, I think I’ve had enough,” said Asa.

I didn’t need him to elaborate—he’d now spent more than 24 hours on the backs of grain cars. The only snag was that our flight home to New York left from Denver in two days, and it would be expensive to change it. At first I said I would do so anyway, but then I backtracked, wavering between being a gentle guide and a steering father. Though it left Salt Lake City at 3:30 a.m., I suggested that we take the next Amtrak east, retracing the route Margot and I had traveled for the Train Test. Asa looked disappointed but said OK.

The California Zephyr (all Amtrak trains have names) was pure luxury. The cars were double-decker, with bathrooms and other utilities at ground level and quiet, cushy seating on the top level. There was a dining car, where we were served breakfast at a table, and a viewing car with large windows offering grand vistas of the desert. So solid and steady and soundproofed was the train that, had we not happened to look out the window as it left the Amtrak station in Salt Lake City, we would not have known we were moving.

I retold Asa the story of not bringing enough to eat or drink on the trip with his mother, and of sleeping in the park at Fruita. Though I had not traveled with Margot over the hump, as hoboes called the Rockies, I was seized by the nostalgic memory of taking that trip with my dad, and I recounted the passage, on the track ahead through many tunnels (including the six-mile, exhaust-filled Moffat), the view of Glenwood Canyon you’d never get from a car, the railroad crossing near the ski area where, as a family, we had waited numerous times for coal trains to pass. Though I should not have, I pitched him on the idea of getting off at Grand Junction and doing the last stretch by freight.… We had enough time, I said. Asa was reluctant. But again he said OK.

Grand Junction, under the proper circumstances, could be an easy place to catch a train. Eastbound BNSF trains would stretch out to the west when their crews changed near downtown. A road ran alongside the tracks. Asa and I bought groceries, refilled our water bottles, and walked. We passed the fences of a big new juvenile-detention facility and finally found a semi-shady spot on dead grass at the edge of a truck lot where we could read and wait.

The problem was, it was very hot—approaching 100 degrees. I was wearing jeans, which I could stand as long as there was shade and a breeze. Asa changed into shorts but even then was uncomfortable. We had a panoramic view of the tracks to the east and west, but there was nothing on them. We endured more than an hour, but then Asa surrendered. “I’m going to wait in the Amtrak waiting room,” he declared. This actually was not such a bad idea—it had been cool there and now would be empty. We’d hear it if a freight rolled in and ought to be able to get where we needed to be in time to catch out. Plus, we could recharge our phones.

The day passed slowly, but at least we were cool. We watched an Amtrak from Denver arrive and disgorge passengers, then watched a little TV. Asa, an avid patron of Chipotle restaurants, told me about a contest they were running—a chance to win a burrito a week for 20 years! A guaranteed stream of burritos is a comforting thought on the rails, where food can run scarce. Another contest: Asa had earned the JanSport U.S. Ski Team daypack I was carrying by sending in 30 Dannon yogurt lids when he was about ten years old. We talked about places where they shout out your name when your order is ready; anticipating that, he and his friend Charlie at the Electric Zoo concert on Randall’s Island had ordered a sandwich under the name Scrotundrus.

At 5 p.m. the station mistress told us that the waiting room was closing. We began a long hot walk to the east side of town, where the Union Pacific assembled trains that left in the evening. But nothing was moving. At a picnic table in a park, we watched thunderheads transform from dark to threatening. Great gusts of wind picked up dust in the yard and dropped it over us, blowing our baseball caps off the table. I suggested we walk a bit more, see if the far end of the UP yard harbored any secrets. Blowing tumbleweeds and trash made the walking unpleasant. Rain wasn’t far off. Asa didn’t need to be convinced when I asked, “Shall we call it a day?”

It was about 20 minutes to the timeworn El Palomino Motel, which we reached just minutes after a gust of wind cracked a large branch off the tree in the courtyard. The worse the storm got, the happier I felt about not sitting on the end of a grain car rumbling up into the Rockies at 30 miles per hour.

In a certain sense, the day had been a waste of time. I had had many such days on the rails, hours spent unpleasantly waiting, waiting, waiting. My son was unaccustomed to this but understood that that’s what it had taken to write a book. The next morning we got up early, rented a car, and drove back to the Denver airport. En route, we stopped to have a soda with my sister and her teenage son. Jeremy seemed envious, eager to try catching out on the fly. He asked if Asa had been scared.

But Beth asked Asa a different question: “What did you learn?”

“Zen patience,” he replied. After the laughter, he added, “And it’s tougher than my dad described in his book.” He continued, to me: “Not in the getting on and off trains, but in the maintaining motivation and having the patience and drive to continue.”

Asa will learn that the friend with whom I took my first big adventure, the bike trip through New England, died at age 23 while mountain climbing in South Africa. His name was Lane Sommer, and his parents showed me the last photographs he’d taken with the camera he was carrying: they featured the rocky mountainside he was scaling and the view from partway up. I’ll never forget them, but I hope not to see them again.

The friend with whom I took my even longer bike ride, across the country at 18, had lost his father when a car struck him on his bicycle a year before our trip, during a family ride. He decided to go on with our adventure anyway.

Death is all around. You take a good look at it, and then you must turn away and carry on. On the rails it seems a little closer; nobody is born there but surely many die. Pistol Pete, the elderly tramp I’d traveled with during my thesis research, was slow and fragile for a place like that. He’d needed a boost from his running partner to climb onto a boxcar. I’d imagined waking up on a brisk Montana morning to find him pale and stiff in his bedroll.

Here’s a different vision of death, more lovely: the loosely spaced conifers on certain winter ski slopes of my youth, the kinds of trees that killed Sonny Bono and Michael Kennedy. I love skiing through powder on these wooded slopes in the Rockies. It’s dangerous, but an instructor in my high school ski club told me the way to do it: Don’t look at the trees, he said. Your job is to focus on the space between the trees. Ski there.

And bring your son.