Of course racism was involved
One possible answer is that, as of the Gold Rush era, Anglos simply began to dominate in Colorado far more than they did in neighboring states to the south, and their prejudices squelched the hyphenated regional cuisine that could have flourished. Food historian and James Beard Award recipient Adrian Miller -- who tells me that one of the earliest area cookbooks he’s come across in his research, from 1901, was written in Spanish -- loaned me a bunch of materials that illustrate what I mean. Think about this excerpt from a white frontiersman’s journal, printed in a 1931 issue of The Colorado Magazine under the title “Diary of a Freighting Trip From Kit Carson to Trinidad in 1870”:
Looked round in the morning and what piles of wagons, oxen and Mexicans. Not one word of English can they speak…These Mexicans are small, thin, dark, dirty, ragged, and generally ugly looking beings...Dined at 11 o’clock on coffee, cakes and fresh meat, cooked in a deep frying pan; each got some coffee in a tin cap and all hands sat round the frying pan and dipped their bread in the pan among the gravy, or rather water and red pepper, and picked the pieces of meat out with their not overclean hands.
Charming, isn't it? No wonder Robert Autobee -- another food historian I spoke with, whose family arrived here from Mexico in 1833 -- had trouble tracing the early history of Mexican-owned restaurants in Denver for a paper titled “No Plato Like Home: Denver’s Slow-Burning Romance With Mexican Cuisine.”
That history starts with chile parlors, which abounded on Larimer St at the turn of the century. According to Autobee, who quotes a 1902 newspaper article, the chile parlors' specialty was not the pork green chile we've come to love, but “a kind of soup, made from beef, beans and chile peppers” -- Tex-Mex-style chili with an “i”. Miller’s documents show it popping up in mountain towns like Telluride, too, where enchiladas, “hot tamales,” and more were being served. But here’s the thing... they were all run by people with names like Dunn and Fitzgerald and Walz. Autobee points to an ad by one Svensk Lunch that proudly proclaims itself “The White People’s Restaurant.” As far as English speakers were concerned, Mexican-run restaurants were “hiding in plain sight,” he says. “They had no phones, they weren’t listed in city directories. Advertising wasn’t in these people’s lives.” This proved to be a smart move, since, by the 1930s, the state government was actively trying to deport them. In other words, in “an era when many Mexican families would quickly replace tortillas with white bread if someone knocked on the door at dinnertime,” per Autobee, Anglos were running the show.
And all this didn’t quite change until the ’50s and ’60s -- which means that, as Mexican restaurateurs here in Denver were finally starting to serve a larger cross section of the population, they were undermined by the sudden popularity of chains that were redefining comida mexicana as a cheap, generic, corporate commodity. Most of them were founded, of course, by gringos -- eventually including Colorado’s best-known homegrown franchises, Chipotle and Qdoba.