Exit 132 off Interstate 29 in Brookings, South Dakota, offers two possibilities. A right turn will take drivers through miles of farms, flatland that stretches to the horizon, cut up into grids by country roads and picturesque barns—a scenic route to nowhere in heartland America. But take a left at the light, and you wind up coasting through a college town of 19,000 that's more than 95 percent white. The city's small Latino minority—less than 1 percent of the population—is mostly students or faculty members passing through South Dakota State University. It was here, in late 2009, that I experienced an epiphany about Mexican food in the United States.

I had been visiting the campus and found myself desperate for a taste of home. For us Southern Californians, that means burritos. Google Maps found me four Mexican restaurants in town. One, named Guadalajara, is a small South Dakota chain with outposts in Pierre and Spearfish. The food there was fine: a mishmash of tacos, burritos, and bean-and-rice pairings. But talk to the waiters in Spanish, and their faces brighten; they trot out the secret salsa they make for themselves but don't dare share with locals for fear of torching their tongues.

The most popular restaurant in town that day was Taco John's. I didn't know it then, but Taco John's is the third-largest taco chain in the United States, with nearly 500 locations. But what lured me that morning was a drive-through line snaking out from the faux-Spanish revival building (whitewashed adobe and all) and into the street. Once I inched my rental car next to the menu, I was offered an even more outrageous simulacrum of the American Southwest: tater tots, that most Midwestern of snacks, renamed "Potato Olés" and stuffed into a breakfast burrito, nacho cheese sauce slowly oozing out from the bottom of the flour tortilla.

There is nothing remotely Mexican about Potato Olés—not even the quasi-Spanish name, which has a distinctly Castilian accent. The burrito was more insulting to me and my heritage than casting Charlton Heston as the swarthy Mexican hero in Touch of Evil. But it was intriguing enough to take back to my hotel room for a taste. There, as I experienced all of the concoction's gooey, filling glory while chilly rain fell outside, it struck me: Mexican food has become a better culinary metaphor for America than the melting pot.

Back home, my friends did not believe that a tater tot burrito could exist. When I showed them proof online, out came jeremiads about inauthenticity, about how I was a traitor for patronizing a Mexican chain that got its start in Wyoming, about how the avaricious gabachos had once again usurped our holy cuisine and corrupted it to fit their crude palates.

In defending that tortilla-swaddled abomination, I unknowingly joined a long, proud lineage of food heretics and lawbreakers who have been developing, adapting, and popularizing Mexican food in El Norte since before the Civil War. Tortillas and tamales have long left behind the moorings of immigrant culture and fully infiltrated every level of the American food pyramid, from state dinners at the White House to your local 7-Eleven. Decades' worth of attempted restrictions by governments, academics, and other self-appointed custodians of purity have only made the strain stronger and more resilient. The result is a market-driven mongrel cuisine every bit as delicious and all-American as the German classics we appropriated from Frankfurt and Hamburg.

Imperialism and Enchiladas

Food is a natural conduit of change, evolution, and innovation. Wishing for a foodstuff to remain static, uncorrupted by outside influence—especially in these United States—is as ludicrous an idea as barring new immigrants from entering the country. Yet for more than a century, both sides of the political spectrum have fought to keep Mexican food in a ghetto. From the right has come the canard that the cuisine is unhealthy and alien, a stereotype dating to the days of the Mexican-American War, when urban legend had it that animals wouldn't eat the corpses of fallen Mexican soldiers due to the high chile content in the decaying flesh. Noah Smithwick, an observer of the aftermath of the Battle of San Jacinto in 1836, claimed "the cattle got to chewing the bones [of Mexican soldiers], which so affected the milk that residents in the vicinity had to dig trenches and bury them."

Similar knocks against Mexican food can be heard to this day in the lurid tourist tales of "Montezuma's Revenge" and in the many food-based ethnic slurs still in circulation: beaner, greaser, pepper belly, taco bender, roach coach, and so many more. "Aside from diet," the acclaimed borderlands scholar Américo Paredes wrote in 1978, "no other aspect of Mexican culture seems to have caught the fancy of the Anglo coiner of derogatory terms for Mexicans."

Thankfully, the buying public has never paid much attention to those prandial pendejos. Instead, Americans have loved and consumed Mexican food in large quantities almost from the moment it was available—from canned chili and tamales in the early 20th century to fast-food tacos in the 1960s, sit-down eateries in the 1970s, and ultra-pricey hipster mescal bars today. Some staples of the Mexican diet have been thoroughly assimilated into American food culture. No one nowadays thinks of "chili" as Mexican, even though it long passed for Mexican food in this country; meanwhile, every Major League baseball and NFL stadium sells nachos, thanks to the invention of a fast-heated chips and "cheese" combination concocted by an Italian-American who was the cousin of Johnny Cash's first wife. Only in America!

In the course of this culinary blending, a multibillion-dollar industry arose. And that's where leftist critics of Mexican food come in. For them, there's something inherently suspicious about a cuisine responsive to both the market and the mercado. Oh, academics and foodies may love the grub, but they harbor an atavistic view that the only "true" Mexican food is the just-off-the-grill carne asada found in the side lot of your local abuelita (never mind that it was the invading Spaniards who introduced beef to the New World). "Mexico's European-and-Indian soul," writes Rick Bayless, the high priest of the "authentic" Mexican food movement, in his creatively titled book, Authentic Mexican, "feels the intuitions of neither bare-bones Victorianism nor Anglo-Saxon productivity"—a line reminiscent of dispatches from the Raj. If it were up to these authentistas, we'd never have kimchi tacos or pastrami burritos. Salsa would not outsell ketchup in the United States. This food of the gods would be locked in Mexican households and barrios of cities, far away from Anglo hands.

That corn-fed Americans love and profit from Mexican food is viewed as an open wound in Chicano intellectual circles, a gastronomic update of America's imperial taking of the Southwest. Yanqui consumption and enjoyment of quesadillas and margaritas, in this view, somehow signifies a weakness in the Mexican character. "The dialectic between representation and production of Mexican cuisine offers a critical means of gauging Latino cultural power, or, more precisely, the relative lack of such power," write scholars Victor Valle and Rudy Torres in their 2000 book Latino Metropolis. (Another precious thought from Valle and Torres concerns Mary Sue Milliken and Susan Feniger, two Midwestern girls who came to Los Angeles and learned to love Mexican food during the 1980s, parlaying that fondness into a series of television shows and books under the billing "Two Hot Tamales." The academics claim the Tamales' success arose from "neocolonial appropriations of world cuisine by reviving a gendered variant of the Hispanic fantasy discourse." Um, yeah…)

With due respect to my fellow lefty professors, they're full of beans. I'm not claiming equal worth for all American interpretations of Mexican food; Taco Bell has always made me retch, and Mexican food in central Kentucky tastes like …well, Mexican food in central Kentucky. But when culinary anthropologists like Bayless and Diana Kennedy make a big show out of protecting "authentic' Mexican food from the onslaught of commercialized glop, they are being both paternalistic and ahistorical.

That you have a nation (and increasingly a planet—you can find Mexican restaurants from Ulan Bator to Sydney to Prague) lusting after tequila, guacamole, and tres leches cake isn't an exercise in culinary neocolonialism but something closer to the opposite. By allowing itself to be endlessly adaptable to local tastes, Mexican food has become a primary vehicle for exporting the culture of a long-ridiculed country to the far corners of the globe. Forget Mexico's imaginary Reconquista of the American Southwest; the real conquest of North America is a peaceful and consensual affair, taking place one tortilla at a time.

I'll never forget the delight I felt a couple of years ago when I worked on a series of investigative stories on Orange County neo-Nazis. One of the photos I unearthed showed two would-be Aryans scarfing down food from Del Taco, a beloved California chain best known for its cheap and surprisingly tasty burritos. The neo-colonizers have become the colonized, and no one even fired a shot.

Tamales and Truncheons

As long as Mexican food has existed in this country, government has tried to legislate it out of existence. This is partly because of stereotypes but mostly because government is government. The resulting underground Mexican food economy, meanwhile, has birthed some of the cuisine's most innovative trends.

In 1880s San Antonio, so-called chili queens—Mexican women who brought the Alamo City national attention by setting up impromptu stalls in city squares to sell fiery bowls of what was then known as chile con carne—began a decades-long game of cat and mouse with local officials. The authorities would declare a certain neighborhood legally off-limits, and the chili queens would shrug and move their tents to the outdoor plaza across the street, bringing with them their legions of loyal customers. It took until the 1940s for San Antonio bureaucrats to formally legalize the street vendors, but only if they subjected themselves to rigorous health inspections and hawked their food from white tents with screens. The public scorned these bowdlerized women, and the chili queens disappeared within years.

The same story arc has played out nearly everywhere in the United States where there has been a Mexican with food to sell. Wandering tamale men spread across the United States during the 1890s until competitors and not-in-my-backyard types convinced city councils to pass laws against them. A century later, loncheras peddling tacos and burritos —first to construction sites, then to anywhere workers take their lunches—have encountered the same protectionism and prejudice. As the public embraces the convenience, affordability, and taste of food trucks, restaurant owners and the city officials they lobby have repeatedly attempted to squash the competition.

Any new businesses in town will always make city planners and councilmen wary and greedy, of course. But the sad, surprising reality is that most of the resistance to loncheras comes from brick-and-mortar businesses. Instead of refining and broadening their offerings to keep up with their new competitors, the incumbents fall back on an argument straight out of a Mafia protection racket: Since we pay more taxes and business fees than food trucks, government should squash our competition so we can continue business as usual.

It's a strategy that has long worked. In 1992 tiny Pasco, Washington, set rules limiting where taco trucks could park and requiring them to pay $45 each month per parking spot. Pasco's restaurants, by contrast, paid only $35 a year for a license. Five street vendors took Pasco all the way up to the U.S. Court of Appeals for the 9th Circuit, arguing that the double standard was unconstitutional, but they ultimately lost. Similar crackdowns have taken place in Fresno (1995), Chicago (1997), Phoenix (1999), and Dallas (1999), where Planning Commissioner James Lee Fantroy sneered during a public hearing on the subject, "The proper preparation of food is one of those things that we must carefully watch. I don't think I could bring my family to one of these [trucks] and feel comfortable."

Even in Los Angeles, the second-largest Mexican metropolis in the world, the majority-Democrat L.A. County Board of Supervisors tried to ban food trucks as recently as four years ago. The city has destroyed carts selling unauthorized bacon dogs and even hauled off some entrepreneurs to jail, despite acknowledging that no bacon-dog customer has ever registered a complaint.

L.A. has a long history of putting the squeeze on Mexican-food peddlers. From 1900 to about 1925, the city council passed resolution after resolution trying to ban tamale wagons from downtown Los Angeles. The tamaleros, knowing what they meant to their legions of customers, fought back. In 1903, when the council tried to outlaw them altogether, tamale wagons formed a mutual-aid society and presented a petition with the signatures of more 500 customers that read in part, "We claim that the lunch wagons are catering to an appreciative public and to deprive the people of these convenient eating places would prove a great loss to the many local merchants who sell the wagon proprietors various supplies." When the city council finally kicked the vendors out as part of the effort to create the sanitized, whitewashed ethnic fantasyland now known as Olvera Street, the vendors just went underground, where they flourished for decades and eventually transformed into loncheras.

In 2008 the L.A. County Board of Supervisors passed a resolution making parking a truck for longer than one hour in unincorporated communities such as East L.A. a misdemeanor with a maximum penalty of a $1,000 fine and six months in jail. The plan sparked a furious backlash—not only among the loncheros, who created La Asociación de Loncheros L.A. Familia Unida de California (Association of Loncheros Los Angeles United Family of California) to defend themselves, but among young bloggers and hipsters who had grown up patronizing loncheras after clubbing or working late. Soon black T-shirts emblazoned with a white lonchera and the statement "Carne Asada Is Not a Crime" flowered across Southern California, and a group of foodies helped the loncheros sue the board of supervisors. A Los Angeles Superior Court judge eventually overturned the supes' diktat.

But it was mostly the will of the loncheros—almost all immigrants who initially came to the United States with no knowledge of English, let alone an understanding of our legal system—that earned the victory. In my homeland of Orange County, Roberto Guzman led a group of loncheros in 2006 to sue the city of Santa Ana to be able to park on city streets from 9 a.m. until 9 p.m., seven days a week. His Cadillac-pink truck "Alebrije's" sells food from Mexico City—buttery, crepe-like quesadillas, massive chili-soaked sandwiches called pambazos, and a concoction of six tortillas covered with sautéed onions, bell peppers, jalapeños, and grilled ham, bacon, and carne asada called alambres.

When the city council (also majority Democrat, and all Latino, making Santa Ana the largest city in the United States with such leadership) sought to negotiate with the loncheros to install a lottery system giving rights to some food trucks but not all, they refused. "Please," Guzmán scoffs. "It would've been favoritism all the way. I felt as if they were going to take away the sustenance of so many families. It was going to be a huge economic loss. And it was too much a worry that, at any moment, [the city] could take away the parking spots from us." Today Santa Ana is a lonchera paradise—and Guzmán owns three of them, with plans for more.

Margarita Millionaires

The self-appointed guardians of Mexican food in this country are right on one point: The popularity of Mexican food has indeed allowed many non-Mexicans to build multimillion-dollar fortunes. German immigrant William Gebhardt created Eagle Brand Chili Powder from the basement of a bar in New Braunfels, Texas, in the early 1890s, parlaying that into a canned food empire that lasts to this day. Glen Bell, founder of Taco Bell, got his idea for hard-shelled tacos from Mitla Café, a San Bernardino Mexican restaurant that stood across the street from Bell's burger stand during the early 1950s. The Frito-Lay company developed its most iconic chips, Fritos and Doritos, by purchasing the rights to those crunchy treats from Mexican immigrants. And Steve Ells, founder of Chipotle, which has mainstreamed massive burritos during the last decade, openly admits he was "inspired" by the burritos sold in San Francisco's famously Latino Mission District.

The easy response to critics of appropriation is that it's the market that decides who gets rich, not ethnic politics. Besides, obsessing over the many gabachos who have become Mexican-food millionaires ignores the many success stories involving Mexicans who displayed the same guile as their pasty-skinned contemporaries.

Larry Cano, for example, started out as a dishwasher at a Polynesian-themed restaurant in the Los Angeles enclave of Encino, worked his way up enough to eventually buy the place, then renamed it El Torito—the chain that pioneered sit-down Mexican dining in the United States. In Texas, the Martinez and Cuellar families created empires with their El Fenix and El Chico chains, respectively, formalizing Mexican restaurants for the rest of the country and essentially creating the genre of Tex-Mex. In Southern California during the 1990s, the Lopez family, immigrants from the southern Mexico state of Oaxaca, helped popularize regional Mexican food in this country, fighting the double challenge of introducing Oaxacan food to both Americans and Southern California Mexicans who looked down on the cuisine as the domain of backward Indians. Today Mexican immigrants are following the Lopez/Oaxacan lead and selling their regional specialties nationwide.

And then there's the story of Mariano Martinez, scion of the Cuellars, who in 1971 created the frozen margarita machine. At his Dallas restaurant Mariano's, which serves heroic enchilada platters, Martinez birthed an empire off the slushy tequila drink, inventing an instant mix that has powered many a house party since. Nowadays Martinez disavows the frozen margarita—he prefers his fresh, with Cointreau. But Mariano's pride in his creation and his cuisine—long dismissed by "serious" food critics as forgettable—remains.

"I've seen them all over the years," he says. "They come in and do this upscale food.…Some of those places aren't there anymore. My little old place I have? Forty years later, we're still pumping the same food. Same phone number. Here I am plugging away at this little Tex-Mex peasant food that no one wanted to play with, that all the ivory tower critics made fun of. And with a drink that no one can resist."

Mariano's original frozen margarita machine is now in the Smithsonian. And Mexican food marches on, a combo plate of freedom giving indigestion to busybodies and authentistas every­where.

Gustavo Arellano, the editor and restaurant critic of OC Weekly, writes the syndicated "Ask a Mexican!" column. He is the author, most recently, of Taco USA: How Mexican Food Conquered America (Scribner).