Farmington is located at the junction of the San Juan River, the Animas River, and the La Plata River, and is located on the Colorado Plateau. Farmington is the largest city of San Juan County, one of the geographically largest counties in the United States covering . The county seat and the other city in San Juan County is Aztec. Farmington serves as the commercial hub for most of northwestern New Mexico and the Four Corners region of four states. Farmington lies at or near the junction of three important highways: U.S. Highway 550, U.S. Highway 64, and New Mexico Highway 371.