San Juan County (/sæn ˈwɑːn/ san-WAHN) is a county in the southeastern portion of the U.S. state of Utah. As of the 2010 United States Census, the population was 14,746. Its county seat is Monticello, while its most populous city is Blanding. The county was named by the Utah State Legislature for the San Juan River, itself named by Spanish explorers (in honor of Saint John).
San Juan County lies at the southeastern corner of the state of Utah. Its borders coincide with the borders of the states of Colorado, New Mexico, and Arizona with Utah. The convergence point of these borders, Four Corners National Monument, is located at the extreme southeastern corner of the county.
The county’s terrain generally slopes to the west and the south, with its highest point, Mount Peale, at 12,726 feet (3,879 m) above sea level. The county has a total area of 7,933 square miles (20,550 km), of which 7,820 square miles (20,300 km) is land and 113 square miles (290 km) (1.4%) is water. It is the largest county by area in Utah.
The county’s western and southern boundaries lie deep within gorges carved by the Colorado and San Juan Rivers. Tributary canyons, cutting through rock layers of the surrounding deserts, have carved the land up with chasms, cliffs and plateaus. In the center of the county are Cedar Mesa, Comb Wash, Natural Bridges and Hovenweep National Monuments. Canyonlands National Park lies mostly within the county borders. The Eastern side of Glen Canyon National Recreation Area / Lake Powell in also in the county.
The Blue (Abajo) Mountains and the La Sal Mountains exceed 12,000 feet (3,700 m) in elevation. Both ranges are covered with lush forests, in stark contrast to the scenery below. The elevation change within the county is from nearly 13,000 feet (4,000 m) in the La Sal Mountains to 3,000 feet (910 m) at Lake Powell, a difference of about 10,000 feet (3,000 m).
The county’s towns lie primarily on a north/south axis along U.S. Route 191 and U.S. Route 163 from La Sal in the north to Monument Valley in the south.