In the area around Matamoros, Mexico, just across the border from Brownsville, Tex., land was selling at $100 an acre only a decade ago—and going begging. By last week, land was up to $5,000 an acre and hard to find. Chief reason : the flat desert lands have blossomed into one of the world's fastest-growing cotton patches, thanks to irrigation from Mexico's Don Martin irrigation project. With the help of U.S. capital, the cotton, boom has also spawned dozens of new industries — and a fine crop of millionaires.
Along the flowered streets of Matamoros'...