Torreóón, with an estimated population of 250 000, is located on the arid-to-semiarid plateau of north-central Mexico approximately 150 miles (240 kilometers) west of Monterrey. The Torreóón metropolitan area includes the smaller cities of Gómez Palacio and Lerdo, which cluster at the mouth of the Nazas River, parts of which are seen northeast and southwest of the urban area. Visible are several infrastructure features—the airport northeast of Torreóón; several roads and railroads; the more highly reflective commercial and industrial section of Torreóón; and a grid street pattern. Outside the urban area, cultivated agricultural fields abound; cotton and wheat are the two main crops grown in the region. During the mid-1900s, this basin was a major cotton-growing area of Mexico. Large mechanized, irrigated farms were developed by tapping into the once-abundant deep wells for ground water; however, in recent decades, farmers have depended on more meager supplies of surface water for irrigation. This region generally receives less than 20 inches (50 centimeters) of precipitation annually. Torreóón is a major railroad center, especially for north-south traffic through Mexico.