Until the Mexican-American War ended in 1848, much of southern Texas was Mexico, and for centuries before that part of the Viceroyalty of New Spain. That’s why, to Mr. Medrano, the heart of Texas Mexican culture is an area that includes southern Texas — the Rio Grande Valley, Corpus Christi and greater San Antonio and Houston — but also part of the northern Mexican states of Chihuahua, Coahuila, Nuevo León and Tamaulipas.Rachel Wharton (New York Times)