Why are there so many mexican food restaurants in Texas?

Im wrting an essay on Texas for school. And in my essay im writing about the Mexican food there and how great it is. I was just wondering why Texas is so famous for Mexican food. Anyone know what i could put in my essay?Why are there so many mexican food restaurants in Texas?
I lived in Texas for 23 years. (over half my life). Almost any non chain place had an extensive Mexican menu, besides American food. And usually it was very good Tex Mex. Since I moved to Florida, I have not found the quality Tex Mex as in Texas. And you would always get free chips and salsa in Texas. It's cultural thing in Texas. Being so close to Mexico, once being part of Mexico. Whatever the reason, they have some great food there !|||We have a large Mexican population considering the fact that we are right above Mexico.|||Because Mexican food is so GOOD and most Texans know a good thing when they see and taste it!|||Because you're so close to Mexico! I got my first taste of real Mexican cuisine when I moved to Arizona for awhile -- WOW! After developing a real taste for it, I found when I moved back East that Taco Bell is not even worth patronizing anymore -- there's just no comparison! I don't eat Mexican unless it's at a GOOD (read "authentic") Mexican restaurant, because the "fast food" places just don't do a thing for me, now that I've had the real thing!|||You could add in your essay that Texas, New Mexico, Arizona and California (if i'm not mistaken) were all part of Mexico, but the United States colonizied and bought them all except Mexico so the US, especially in Texas as deep rooted ties in Mexico so the culture and delicious food is tied together.|||Number one is the percentage of mexicans in Texas...that opens up another topic all together but that is the reason. That and it is really cheap to open one!!!!|||umm, the close proximity to mexico perhaps?|||Because there are so many Mexicans there and they like it.