The carnitas , frizzled a deep brown from braising in fat, have fibers that splay open as I chew. The pinto beans are earthy and soft, the pico de gallo a dense hash. The fresh avocado option, essential here at La Taqueria in San Francisco’s Mission District , unifies everything in a buttery medium where the line between flavor and texture is indistinct, irrelevant. I’m still sweaty after a four-block jog from the nearest parking spot on a Saturday night, but I don’t care because the burrito my friends have waiting is as good as it’s always been, since my first time here three decades ago. I can even look past the evil eye of the woman peeved about my friends hogging a table. To find a seat at perennially jammed La Taq you face the kind of public aggression that this historically chilled-out city isn’t known for—except when it comes to scoring one of the best burritos in America.

You see a mix of old and new Mission here, friends in their 20s loitering with coworkers over Tecates, and older couples in their black-and-orange Giants caps, stopping on the way home from a day game. There are plenty of out-of-towners, people who left the Bay Area and still come back to Le Taq as soon as their flights land at SFO, and others checking items off their tourist to-do lists: In 2014 Nate Silver’s ESPN-owned statistics website, FiveThirtyEight, chose this as the winner of its nationwide burrito bracket .

It’s hard to believe in this age of the burrito emoji, but before the ’90s, burritos existed mostly in Latino neighborhoods like the Mission. The ones that crossed over were visitors from other worlds, folksy Tex-Mex (BurritoVille in Manhattan) or California exotic (Tortillas in Atlanta). Then Chipotle happened. The chain’s founder, Steve Ells, was a line cook in the 1980s at Stars, Jeremiah Tower’s flashy San Francisco brasserie. Like most local 20-somethings, he faced down many, many burritos; Ells would sometimes grab one before his shift at the restaurant. “I had grown up in Boulder,” he recalls. “A burrito looks totally different in Colorado—or did.” Ells was mostly influenced by the form of the burrito, its self-containedness. So he opened his first Chipotle in Denver in 1993; within a month that shop was selling more than a thousand Mission-style burritos a day. A second outpost opened, then a third, then eventually 2,000 more stores, spreading Ells’ generic version of this local specialty throughout the country.

Here in its native habitat, though, the Mission burrito is still lithe, still expressive, each one different from the other. There are burritos for drywall men and tech bros, skate punks and tourists, for luxury condo dwellers and drunks. Some raise a fist for Chicano pride, others are coded for bougie bohemians. Some are the batons for the city’s current relay sprint toward gentrification; others live on as they have despite the pressures of a city in full-on boom. Most—and I say this as a man who has been eating burritos in San Francisco for more than 30 years—are delicious.

But in a city where the average monthly rent for a one-bedroom apartment in 2016 spiked above $3,600, these burritos face an existential challenge. San Francisco is shedding blue-collar workers and Latinos at a rate that has affordable housing advocates freaking out. Last year the city released a report showing that the Mission’s Latino population fell from 60 percent in 2000 to about 48 percent. The same data projects Latinos could make up just 31 percent of the historically Latino district by 2025. Yet the Mission remains a place you cannot understand—or even enjoy—without the burrito, even as the streets where it was born become disturbingly high-end. So how does a cheap, working-class food endure in a place that’s suddenly neither?

You take the BART train to 24th Street and make your way past the homeless and the loitering high school kids to get to El Farolito. There, you’ll eat a burrito that shows you what the ones in other cities are not.

The carnitas in an El Farolito super burrito is savage and salty. It dominates the tubular form the way a 24-ounce T-bone commands a plate at Ruth’s Chris: without equivocating, apologizing, or making excuses to vegans. The sheer volume of pork makes the orange grains of Mexican rice they’re packed with recede. Avocado slices are necessary, just as crema , a cooling squiggle, seeps through the thick clump of ingredients. This is one of the defining burritos in the Mission style. This is one of the great burritos of San Francisco.

A Mission burrito starts with a large flour tortilla, typically steamed on a press like a laundromat’s. Then it’s filled egg roll–style with Mexican rice, beans (black, pinto, sometimes refried), salsa, and some chopped or shredded meat ( carnitas , grilled or stewed chicken, carne asada, or offally things like tongue, chitterlings, or brains). It is universally known that “a super,” which costs a buck or two more at each place, gets you a handful of cheese, sour cream or crema , either guacamole or sliced avocado, sometimes shredded iceberg.

The twang of these ingredients is what sets the Mission’s burritos apart. Carnitas can be merely steamed pork in other places; beans can be canned or boiled lifeless; the guacamole scraped from a Sysco bucket. But there are hundreds of places selling burritos in the nearly 1.5 square miles of the Mission. To compete, owners must stand out, the way the roasted tomato salsa does at Papalote , or the al pastor does at Taqueria Cancún . Other places can have good burritos, but they don’t have a culture of good burritos, a community of strivers.

The burrito maker—often a she—folds in the tortilla’s ends and compresses the fillings into a fat, even cylinder as she rolls. That roll is everything. El Metate is known for its tight game. (But once, at a tiny Oakland burrito shop, Taqueria Las Comadres, I watched a woman roll the excess flap of tortilla into a crisp, chewy spine then embed it to run the length of the filling. It was a move of staggering artistry.) An optional turn on the griddle to crisp the tortilla’s outer skin—what the menu calls dorado-style at La Taq—and then the burrito maker sheaths it in foil, pinches the ends, and drops it onto a plate or red plastic basket alongside a handful of chips.

The Mission burrito is a thing so fused to California’s relationship with Mexico that its evolution is nearly impossible to chart. You can see the embryo of it in the burrito de carne , the rolled taco of Sonora in northern Mexico. It’s plausible that some version of that spread to California through proximity. But the Mission burrito is specific to San Francisco, and a thousand miles of mutation separate these from the ones in Sonora.

San Diego has what it calls, with bombast, the California burrito. It matches in heft, except its bulk comes from fries, which kicks it closer to drunk food. The breakfast burrito, reportedly born in Santa Fe in the 1970s, is a hyperbolic blowup of Austin’s breakfast tacos. And the Tex-Mex wet burrito, ladled with enchilada sauce, is a clunky scan of enchiladas suizas . Simply put, California’s burritos are better than other states’ burritos, but none are as good as San Francisco’s. (I’m aware of the controversial nature of this truth.)

Los Angeles has spare, delicious burritos, sometimes only beans and meat, like the frozen ones you buy at 7-Eleven. San Francisco hardcores say they’re weak; Los Angeles hardcores think Missions are vulgar. Los Angeles Times food critic Jonathan Gold once called San Francisco burritos “monstrous things wrapped in tinfoil, and filled with what would seem to be the contents of an entire margarita-mill dinner.” It’s hard to defend the aesthetics, except that a good Mission burrito requires talent. It’s as dependent on proportion, balance, and ingredient quality as pastrami on rye or a bowl of ramen. It’s just…big.

That girth has fueled their appeal since the beginning. Burritos are Chicano roots food, born as rations handed out to pickers at the huge produce farms in the central state. In the 1960s, restaurant consultant Peter Garin was working the lettuce fields. “I remember the texture of the shredded beef,” he told SF Weekly in 1993, recalling field burritos, “the heat of the green peppers, and the proper proportion of rice and beans.” You didn’t need a fork, or even clean hands.

Taqueria la cumbre is one of two places in San Francisco that says it invented the Mission burrito, down to the exact day: September 29, 1969 (the other, El Faro , claims an earlier date: September 26, 1961). La Cumbre’s Number Six, a regular with carne asada, was my burrito initiation. It was back in the 1980s; I had moved to San Francisco from Berkeley with a few crates of English-lit paperbacks and some Hefty bags of clothes.

That carne asada burrito was one of the first things that sold me on the potential of cheap food. It demonstrated how a few basic ingredients can become perfected—unpolished, but perfected. You peeled back the foil and chewed at the compressed magma of grilled skirt steak with soft ranchero beans and rice rolled up in a flour tortilla with a slice of Jack cheese. It was large enough that you could feed like a ball python; after finishing, your body could forgo a few meals.

Today I’m a couple of bites into the loose roll of carne asada, shedding pale amber rice onto my plate, and La Cumbre feels like a place with its best burritos behind it. Same for El Faro, its historic rival. San Francisco’s first generation of burrito creators is kind of like Madonna. The old fierceness is gone, but she’ll always have your respect, even when she face-plants on stage. Don’t worry, girl: In my heart, I’ll always pick you up.

La Cumbre’s sign juts out onto Valencia Street, its heavy black Mexican Gothic font looking defiant, like a collarbone tattoo with three-inch letters. It’s at odds with the Valencia of 2016, a row of restaurants and boutiques with prim fronts and minimal signage, coding for the expensiveness within.

Of course, as with the rest of San Francisco, there’s been a push to recast the burrito in upscale terms. In Hayes Valley, a central neighborhood that’s in the throaty flush of trending up, I order a duck confit burrito at Papito Organic Mexican Cuisine. When I take a bite, it spills a pile of duck slicked with sugary mole, unloading so much confit that I worry about the number of birds compelled to sacrifice their legs. It’s not bad, but it smears the original, dresses it up in a summer-weight linen blazer to accessorize the Mission right the hell out of it. I notice that the guys cooking are behaving just like the ones at El Farolito, though the confit they’re heating up is a dubious update of crisp carnitas . Good for them, I think, working their way up. But I wonder what they think of this burrito.

Another, bleaker, version is a burrito I sample at ground zero of the tech capital that San Francisco has become: Twitter’s headquarters. The Mission burrito is a pillar of that company’s origin story.

In 2006, lore goes, Jack Dorsey and a couple of buddies ordered burritos. It was then, while peeling back the foil, that Dorsey shared his vision for the social network. (Now Twitter’s CEO, he declined to be interviewed for this story.)

The Market is a public food hall on the ground floor of the Twitter building. I order a chipotle chicken burrito from its taqueria, Taco Bar, and find a table outside. As millennial tech workers cruise by in their workout gear—guys wearing Vans with high socks, backpacks with logos for companies like Uber and Optimizely, vintage striped basketball shorts—I face the worst burrito of my life. The tortilla is stiff and cold. I get a mouthful of frigid sour cream in one bite and then slack white-meat chicken embalmed with cumin.

I drop its heavy remains in the compost can, pick my way past young bearded guys wearing chambray shirts, and escape.

Bearded bros are nowhere in sight on the Mission Street sidewalk in front of El Castillito . There’s only a mighty cliff of a man, sucking at the remaining inch of what must have been an epic blunt. Nearby, businesses sell car insurance and cheap bleached jeans—this is the kind of place where the Mission burrito was nurtured.

Since the 1950s, when the neighborhood started to change from Irish and Italian to Mexican, the Mission has been a place known for its texture. There’s physical texture, in the crates of bruised plantains and shiny yuca fronting corner markets. But also cultural: the overlap of Latino and gay, wealthy and not, tagged-up and mural-covered. It’s the San Francisco of cultural compression, which is the best San Francisco. You can’t blame Facebook’s Mark Zuckerberg and all those condo buyers for wanting to live here. It’s nice, and it’s got a real patina—despite changing demographics, classic places like El Castillito haven’t been squeezed out.

Inside, a guy with a sparkly ear stud leaves the cash register, walks toward the ceiling-mounted TV, and flicks the remote at it. A telenovela flashes on. “ Ay güey !” he says, clicking his tongue at the screen. He jabs the remote again and the Giants-Padres game stutters into focus. Half a dozen men slouching over burritos turn toward the screen, all speaking Spanish.

The cook reaches for a gob of al pastor from a bin on the line, spreads it down a tortilla piled with orangey Mexican rice and black beans (“You want espicy or mile?” he asks, salsa ladle poised), then twists it in foil.

El Castillito didn’t make it into FiveThirtyEight’s greatest-burrito bracket. But Gustavo Arellano , a member of the selection committee and author of Taco USA: How Mexican Food Conquered America , loves these burritos—so much, he says, that he felt they were too personal a choice to lobby for. Chef David Chang , another voter, stopped by after the bracket was set. “I don’t know,” he said at the time. “It might be the best burrito I’ve ever eaten.” Anna Maria Barry-Jester , the bracket’s author, called it the one that got away. I’ve been eating in San Francisco for decades, and I’ve never made it here. I feel sort of ashamed.

I call Arellano to ask why a place that makes such good burritos has kept such a low profile. “Because it stayed resolutely working class,” he says. “There’s ones that become Instagram and Yelp sensations, and then ones that are better.”

The pastor pork is crisp around its dark edges, chewy, animated by a charge of vinegar and heat that bucks like a gun in recoil. The rice has tooth, the beans a fine grain. There’s a satisfying tightness to the roll, it feels good in my hand, and it cost less than ten bucks. This could be the best Mission burrito in San Francisco. This could be the best Mission burrito in the world. Damn, I’ll go Chang one better: This is the best burrito I’ve ever eaten.

Maybe it’s survived, with original Mission soul intact, by building enough of a wall to obscure it from the tourists, the techies, and the condo buyers. That’s some irony: The most authentic Mission burrito is also the most obscure. Long may it roll.