Uvalde County is located in southwestern Texas, including part of the north margin of the Gulf Coastal Plain and the south margin of the Edwards Plateau. Its principal mineral resources are asphalt rock, clay, limestone, gravel, trap rock, and surface and underground water. Some shows of oil and gas have been found at several localities, and small production of oil has been obtained on the Pulliam ranch in the southern part of the county. The Southern Pacific Railroad crosses the county east-west, the San Antonio, Uvalde & Gulf Railroad of the Missouri Pacific System enters from the south, and the Uvalde & Northern Railroad extends from Uvalde up the Nueces River Valley to Camp Wood in Real County. The surface elevation varies from about 800 feet above sea level at the south side of the county to 1,700 feet or more in the northern part.