Amarillo is located near the middle of the Texas Panhandle and is part of the Llano Estacado or Staked Plains region which has a surface that is relatively flat and has little drainage in the soil. Due to the lack of developed drainage, much of the rainfall either evaporates, infiltrates into the ground, or accumulates inplaya lakes. According to the United States Census Bureau, the city has a total area of 90.3 square miles (234 km2), with 89.9 sq mi (233 km2) of it land and 0.4 sq mi (1.0 km2) of it (0.50%) water. The Amarillo metropolitan area is the 180th-largest in the United States with a population of 236,113 in four counties: Armstrong, Carson, Potter, and Randall.
About 20 miles (32 km) northeast of Amarillo is the Canadian River, which divides the southern part of the High Plains to form the Llano Estacado. The river is dammed to form Lake Meredith, a major source of drinking water in the Texas Panhandle region. The city is situated near the Panhandle Field, in a productive gas and oil area, covering 200,000 acres (800 km2) in Hartley, Potter, Moore, Hutchinson, Carson, Gray, Wheeler, and Collingsworth counties. The Potter County portion had the nation's largest natural gas reserve. Approximately 25 miles (40 km) south of Amarillo is the canyon system, Palo Duro Canyon.
The underground structures known as Amarillo Mountains are an extension of the Arbuckles of Oklahoma and the Ouachita of Arkansas and Oklahoma. They are some thousands of feet underground. The range was discovered by pioneer oilmen. Some of the peaks are believed to be 10,000 feet (3,000 m) high. The tallest peak is reported to be 2,500 feet underground in northeast Potter County under the Alibates National Monument.