The asymmetrical relationship between American and Mexican border regions is nonetheless relatively recent. Until the twentieth century, both sides of the border were, in the jargon of today’s economists, underdeveloped out-of-the-way towns of little consequence to the financial capitals of Mexico and the United States. The border, in the eyes of most Mexicans and Americans, was still a frontier. For the United States, that began to change in the late nineteenth century, when the arrival of the Santa Fe and Southern Pacific Railroads opened the Southwest to mining and commercial agriculture and linked the cattle ranches of Texas to the stockyards of Kansas City and Chicago. Still, disparities between the American and Mexican borders were merely getting underway.