Cotton, crucial to the economy of the American South, has also played a vital role in the making of the Mexican north. The Lower Río Bravo (Rio Grande) Valley irrigation zone on the border with Texas in northern Tamaulipas, Mexico, was the centerpiece of the Cárdenas government’s effort to make cotton the basis of the national economy. This irrigation district, built and settled by Mexican Americans repatriated from Texas, was a central feature of Mexico’s effort to control and use the waters of the international river for irrigated agriculture. Drawing on previously unexplored archival sources, Casey Walsh discusses the relations among various groups comprising the “social field” of cotton production in the borderlands. By describing the complex relationships among these groups, Walsh contributes to a clearer understanding of capitalism and the state, of transnational economic forces, of agricultural and water issues in the U.S.-Mexican borderlands, and of the environmental impacts of economic development. Building the Borderlands crosses a number of disciplinary, thematic, and regional frontiers, integrating perspectives and literature from the United States and Mexico, from anthropology and history, and from political, economic, and cultural studies. Walsh’s important transnational study will enjoy a wide audience among scholars of Latin American and Western U.S. history, the borderlands, and environmental and agricultural history, as well as anthropologists and others interested in the environment and water rights.