Tex-Mex food was developed from Mexican and Anglo influences, and was traced to the late 19th century in Texas. It still continues to develop with flour tortillas becoming popular north of the border only in the latter 20th century. From north to south, much of the influence has been related to food industrialization, as well as the greater availability overall of food, especially after the Mexican Revolution. One other very visible sign of influence from the United States is the appearance of fast foods, such as hamburgers, hot dogs and pizza.