Walking every street in San Francisco seemed an endless task. Pieced together, the pavement would stretch all the way from here to Juarez, Mexico.

Only a handful of people have done it. And now I can say I have. All 2,612 streets.

I have seen this city from every hilltop. Visited every neighborhood. Walked every street - from First to 31st. From Second to 48th avenues. From A Street to Zoo Road. From the bay to the Pacific. From the Golden Gate to the San Mateo County line.

It took more than 500 hours during a seven-year period.

To cover the city's 1,260 miles of streets, I went the extra mile. A few hundred extra miles, actually. Cul-de-sacs and detours around hills add up. So do return trips to the car. I traveled a total of 1,500 to 2,000 miles.

Averaging about 3 mph, figure about 500 to 700 trips to get the job done.

A frayed and scotch-taped street map that I carried in my back pocket recorded my progress. A red felt-tip pen traced the streets completed. Each time, I picked up from where I left off.

It was nuts. Totally obsessive-compulsive. Call it an exercise in eccentricity or futility, and you'd probably be right.

I couldn't say exactly how many miles I covered, because I didn't carry a pedometer. Although I prefer walking unencumbered, I managed to take about 5,000 photographs on my perambulations.

I chased my shadow all over San Francisco. Watched it cast down hillsides on sunny days ... against the gray concrete sidewalk, the asphalt street, stucco and brick houses, on the sands of Ocean, China and Baker beaches.

Most of the time, I walked alone. But on occasion, friends and family would accompany me. My patient wife, who joined me on many occasions, liked to check out the neighborhoods and the hilltop views. She particularly liked eating at cafes, delis, pizza joints, taquerias, restaurants and bakeries along the way. There are more than 3,000 of them in the city.

I did this walk primarily to get some exercise. To learn what I could about a place I still call home. To see and absorb as much as possible. To live in the moment.

As a native whose family history in the city goes back to the 1860s, I am very attached to my hometown. Yet I haven't lived here since Joe Alioto was mayor. I have commuted to work here for 25 years. So I look at the city, in some respects, as an outsider. I see the city in a new light each day from the Golden Gate Bridge. And for the past seven years, I have been one of its most devoted hometown tourists.

My view of this city has been shaped by my mind's eye at 3 mph. And 150 years of family history.

I found that walking every street in San Francisco requires dogged determination and single-mindedness. It results in sculpted calves, sore feet and a greater sense of place. It sometimes involves trips to the podiatrist, acupuncturist and shoe store. I went through a half dozen pairs of shoes.

Some streets are long, some short. Some wide, some narrow. The longest is Mission Street (7.29 miles within city limits). The shortest is Richter Avenue (14 feet). Sloat is the widest (135 feet across) and DeForest is the narrowest - only 4 1/2 feet wide. I could touch both sides with my outstretched palms.

Many aren't streets at all; they are alleys, avenues, boulevards, circles, courts, drives, lanes, loops, places, plazas, roads, terraces and ways.

You name it, I've walked them all. Well, almost.

"A number of city streets lie underwater in the bay," says Mike Wynne, geographic information system business analyst for the San Francisco Planning Department. Apparently, some parcels and streets were mapped out before the shallow parts of the bay were filled in.

"There are a number near Candlestick Point," Wynne says. "They are no doubt of little relevance to your project. ... I'm sure nobody would expect you to walk them."

I had to let some things go, including the underwater streets and a few streets that were gated and locked.

Along the way, I discovered many streets that weren't on the map and others that were on the map but no longer exist (streets that had been built or eliminated after my map was printed).

Most of the time, I walked in the street because asphalt is easier on the feet and joints than concrete sidewalks. Streets also provide better views.

For the past year, I concentrated on walking Bayview-Hunters Point, Visitacion Valley, the Hunters Point Naval Shipyard, Treasure Island, Yerba Buena Island and the alleys in Chinatown, North Beach, downtown, Russian Hill, Telegraph Hill, South of Market and the Mission.

I was able to walk the projects unmolested from early morning until about noon, when few people were out. I did the most dangerous streets in inclement weather.

On foot, one can feel exposed in tough neighborhoods. A 6-foot-4 white guy with male pattern baldness walking up and down Sunnydale or Oakdale streets sticks out like a cheap toupee. Several people thought I was an undercover cop.

On several occasions, near the end of my walk, I tried unsuccessfully to stroll past the guards at Hunters Point Naval Shipyard - a 500-acre toxic waste Superfund site.

I was curious about the fenced shipyard, which I had seen from the top of Candlestick Hill and from the end of Marlin Court in Hunters Point. In the distance, hard-hatted workers in earthmoving equipment scurried around like a disturbed ant colony.

When the artist community just inside the fenced compound had an open house one weekend, I sneaked in.

The shipyard resembles a ghost town. Streets empty. No street signs. Mazes of chain-linked fences topped with barbed wire block roadways. Long-abandoned buildings with broken and boarded-up windows and peeling lead paint line street corridors. Broken-down wharves are occupied by brown pelicans and seagulls. An eerie silence hangs over this once thriving World War II shipbuilding mecca.

I trespassed in the shipyard three times and twice was invited to leave by security guards.

Signs read: "Caution: Hazardous Wastes." The list of toxic substances is long and hard to pronounce. I probably should have been wearing a Hazmat suit.

Man-made Treasure Island is not much different. Talk about prime real estate that's been trashed by neglect. The Navy was not a good landlord there either. Knock-your-socks-off views of the city and bay are marred by hazardous-waste warning signs posted on chain-link fences that surround boarded-up, dingy blue, gray and beige clapboard apartments. Not a store or place of business in sight.

Yerba Buena Island, a wooded hill sticking up out of the bay, is the midpoint for the Bay Bridge. Dangerous on- and off-ramps make this island and adjoining Treasure Island a challenge to reach. Its streets, architecture and landscape are reminiscent of the Presidio. It offers terrific views of the bridge, the city and the East Bay. Right now, the east end of the island is a series of detours as construction crews overhead work on the "S" curve.

The alleys of San Francisco are intriguing but present some unique challenges, too. Left until last, they were inefficient to walk.

Scattered mostly around Chinatown, North Beach, Russian Hill, South of Market and the Mission, these short, often dead-end streets resemble alleyways, despite their official names. They are a throwback to old San Francisco. These narrow corridors offer intimate views of living rooms, kitchens and backyards ... clothes hanging on lines or on wire hangers in open windows ... potted plants on sills reaching for the sun. They're places where cats loiter. Where wires stretch like cobwebs from pole to house.

At times I felt like a ghost walking these streets. I imagined myself gone and others following my footsteps.

I saw some of the same windows that Jack Kerouac saw in "On the Road" - "the really crazy windows that made faces at me" and "the ones with shades drawn that winked at me."

And from some of those windows, like Kerouac, I smelled the savory side of San Francisco. "The seafood places along Fisherman's Wharf ... the chow-mein-flavored air that blew from Chinatown ... the spaghetti sauces from North Beach."

I was reminded of the Beat writer a few times. On Jack Kerouac Alley, between Vesuvio and City Lights Bookstore, I came across a brass-lettered quotation of his embedded in concrete:

"The air was soft, the stars so fine, the promise of every cobbled alley so great, that I thought I was in a dream." A crushed cigarette butt punctuated the quote.

I had similar experiences with other literary figures: a plaque at the corner of Third and Bryant streets marking the spot where Jack London was born; alleys named after Richard Henry Dana, Mark Twain, Bret Harte, Frank Norris, Ambrose Bierce and William Saroyan honoring their residency here.

There are 5,321 blocks in the city. The two biggest are the Presidio (block No. 1300) and Golden Gate Park (block No. 1700). Although I've walked every block in San Francisco, I haven't been to the Farallon Islands or Red Rock ... or Alcatraz. All within the city limits.

The more I walked, the more I realized how little I know about my hometown.

Environmental poet Wendell Berry put his finger on it when he wrote: "If you don't know where you are, you don't know who you are." I guess that's what I've been trying to figure out.

Wallace Stegner's essay "Sense of Place" put it this way:

"A place is not a place until people have been born in it, have grown up in it, known it, died in it. ... Some are born in their place, some find it, some realize after long searching that the place they left is the one they have been searching for."

I started this project at age 54. I'm 62 now. I retired from my full-time job and became a grandfather along the way.

I can truthfully say, "I've been around the block."

I've walked by every house, school, church, synagogue, mosque, corner grocery, department store, apartment building, condo, high-rise, warehouse, firehouse, police station, park, lake and playground ... past every telephone pole, sidewalk crack, pothole, manhole, cistern, stop sign and stoplight. I've passed the majority of the city's 215 landmarks, mostly in ignorant bliss.

I've watched people paint and remodel their homes. Tunnel under a Victorian to build a garage. Build new homes and tear down old ones. I watched the dismantling of the Emporium and its transformation into Bloomingdale's. I saw Letterman Hospital implode and George Lucas' Letterman Digital Arts Center in the Presidio sprout in its place. I watched the Embarcadero Freeway (which my grandfather helped build) come down, and witnessed the relandscaping of the area.

I realize that my exploration of San Francisco is not over.

"We shall not cease from exploration," T.S. Eliot wrote, "and the end of all our exploring will be to arrive where we started and know the place for the first time."

I was born in San Francisco, but did not know my place. I've got a much better sense of it now.

Nothing is forever, though. I can only claim to have walked every street in this city at this moment in time. New streets are being built as I write.

But this crazy project is over. I'm now a retired street walker.

Temporarily, though, I can say this: If you live in San Francisco, I've walked by your house. {sbox}