Checking, it seems he says he hadn’t had it before on a visit to Los Angeles in 1962. However, in the following episode he visits Anna’s house which suggests he had been to southern California before.
I am looking at a Better Homes and Gardens cookbook that I have. It has recipes for Mexican Rice, Cheese Enchiladas, Guacamole and “Chiles” Rellenos. I got it from my mom and the copyright date is 1959.
The OP and thread title ask when this type of food became “mainstream” in the USA. Better Homes and Gardens is pretty fricking mainstream if you ask me. I will admit, the recipes have a certain, shall I say, oddness to them. There is no mention at all of jalapeno peppers or even chili powder for that matter. One recipe does use cumin seed.
The Cheese Enchilada recipe is very amusing and sad actually:
“Sprinkle enchiladas (from can or frozen package) with shredded sharp process American cheese. Heat according to label directions. Trim with olives speared on toothpicks.” The fact the editors of BH&G reference canned or frozen enchiladas in a 1959 cookbook makes me think this wasn’t some super exotic item. There is also a recipe for a “Quick Chili Supper” elsewhere that calls for using an 11-ounce can of tamales. Again, the availability of canned items makes me say this was mainstream at this point.
My guess is some GIs were exposed to Mexican food during or shortly after WWII when they were stationed in California. This would have helped spread popularity across the US.
Mom made tacos when I was a kid in the 80s. Boxed taco shells & seasoning packet with ground beef. I fondly recall using a lot of Louisiana hot sauce on them as I grew older and started to enjoy spicy foods. I might pick up a kit to try it again after all these years.
The very first Mexican restaurant I remember is Naugles, though it’s a pretty distant memory.
I’d swear that there was still a Chi-Chi’s around here but the map shows it’s a Pepe’s, a regional chain with 40 locations. I’m a little curious but with so much great Mexican food available here in Chicago, the odds are I’ll never step foot into the place.
Hehehe, good Tex-Mex is usually around 1000 calories a bite, as well.
Nope, I had a huarache instead…mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm. 
Not to be confused with Huitlacoche.
Also mmmmmmmmmmmm… Great in a quesadilla (like the fried masa style.)
Bean & Cheese Cup! Represent!
Actually, fried implies oil. I mean masa cooked on a dry griddle/comal, as opposed to the folded over or stacked flour tortilla style.
My sister’s first husband was the manager of one (possibly the first) Taco Bell to open in the early 70’s in Hawaii. He brought over a bunch of food that was very different from what’s available today (remember the Bell Beefer) for us to try. My Dad said tacos would never take off in Hawaii! 
Prior to that, my sisters and brother ate tacos somewhere around the University, but the only taco makings available, were frozen taco shells with seasoned beef (ala Jack in the Box tacos). AFAIK, there was no taco sauce or salsa back then. “Taco sauce” was either tabasco sauce straight or mixed with ketchup.
As I think about it. The beef in frozen tacos was shredded, not ground and kind of tough. Also, cheese was American. Cheddar cheese was too exotic, coming only in blocks or from the huge cheese wheels at Woolworths!
Spending almost all my life in California and Arizona, I have no idea what the OP means about ‘becoming’ mainstream. When I was a kid in Phoenix we had a Mexican-style fast food place with a giant sheet metal sign of a stereotypical Mexican kid holding a taco. The kid’s eyes were cutouts and the pupils were on a sheet that moved back and forth behind them. We never ate there, though; the only time we ate out was when we were on a trip.
Los Angeles has had chili joints long before I was born and San Antonio’s chili queens alluded to above were long before that.
OTOH I had also had no idea about deep dish pizza until recently.
The story I’ve always heard was that when it opened in 1969 the locals were concerned it would not be in business long since there weren’t many Mexicans in town to eat there.
I came across this photo, said to be from the Pacific National Exhibition in Vancouver in 1977.
Hard to define “mainstream” but I find this story of a Muslim immigrant going from the West Coast to Wyoming, exploiting a late 19 century tamales craze, in early 20th century Wyoming and, creating a regional hotel family dynasty amazing.
All I can say is WOW. Thanks for sharing one of the most amazing articles I’ve read in a very long time.
I think one measure of mainstream is this. Who eats there? Mexican restaurants in my area (NW of Chicago) have always had a large proportion of non-Hispanic customers, even the good ones, and this has been true for a couple of decades. A good Indian restaurant is as easy to find, but much less likely to be filled with obvious white people.
Of course, I commonly sit in the window at my favorite restaurant and watch people enter the Panera next door, or get invited to a work birthday lunches at Olive Garden, but then on the other hand I might as well say “We descended from monkeys, so why are there still monkeys?”
And take with salt, it’s certainly completely anecdotal.
When my Family of Origin moved to the big city of Joplin MO in 1966, there was a single Mexican restaurant, called Casa Montez. It seemed incredibly exotic, but I never ate there since my family couldn’t afford to eat out. I wondered then, and still do, why the Montez family would choose to live as the only Mexicans in the city, even if their restaurant made them fabulously wealthy.
Today there are at least a dozen Mexican places in Joplin. Casa Montez is still there. It opened in 1965 and is billed as “Joplin’s oldest locally-owned restaurant”.
Trip Advisor’s list of best Mexican restaurants in Joplin includes Taco Bell, and a reviewer has commented, “It doesn’t get any better than Taco Bell”. My favorite review, however, is “Just like every other Taco Bell”.
I originally searched for “Joplin MO casa de Montez” and got back exactly one result.
There’s a name for the rare one-result search, but I can’t remember it. This is the first time I’ve accomplished it. The result was not the restaurant I was looking for.
The term is “Googlewhack”, although it technically refers to a string consisting of exactly two words.
Louis Henry Stermburg was the co-founder off Patio frozen foods in San Antonio in 1948. He got the idea (as Kolak suggested above) to sell tamales and chili to former airmen who had been stationed in SA.
I imagine the same thing happened elsewhere.
Mexican food and Tex Mex seem to have always been part of the landscape here, but I have a clear memory of my grandmother ( a very adventurous eater) took me to a Chinese restaurant in Midland, TX in 1973. I’d never been to one of known anyone who’d been to one.
Tamales are interesting… apparently there were itinerant Mexican farmhands who worked in the South in the very early part of the 20th century, and they made tamales from the local ingredients- cornmeal instead of masa, etc…
Local black farm workers developed a taste for them, and started making their own style.
Here’s an article on it:
Meanwhile, in border areas, tamales were popular street food in Texas and the Southwest, much like chili was.