The Valley of South Texas is a region of puzzling contradictions. Despite a booming economy fueled by free trade and rapid population growth, the Valley typically experiences high unemployment and low per capita income. The region has the highest rate of drug seizures in the United States, yet its violent crime rate is well below national and state averages. The Valley's colonias are home to the poorest residents in the nation, but their rates of home ownership and intact two-parent families are among the highest in the country for low-income residential areas. What explains these...