"While Mexicans and Americans moved freely back and forth across the boundary line, by the late nineteenth century a series of new U.S. laws restricted a growing number of immigrants from crossing the border," St. John wrote. "The U.S. Congress passed the first law restricting immigration — specifically that of convicts and prostitutes — in 1875. By 1910 new legislation had added Chinese immigrants, lunatics, people likely to become public charges, contract laborers, polygamists, anarchists, and others deemed undesirable to the list of excluded groups. This legislation turned what had been an innocent movement of people into illegal immigration."