The Metropolitan Water District of Southern California is a regional wholesaler and the largest supplier of treated water in the US. The name is usually shortened to "Met," or "MWD." It is a cooperative of 14 cities and 11 municipal water districts and one county water authority that provides water to 19 million people in its 5,200-square-mile (13,000 km2) service area. It was created by an act of the California Legislature in 1928, primarily to build and operate the Colorado River Aqueduct. MWD became the first (and largest) contractor to the State Water Project in 1960. Metropolitan owns and operates an extensive range of capital facilities including the Colorado River Aqueduct which runs from an intake at Lake Havasu on the California-Arizona border, to an endpoint at Metropolitan’s Lake Mathews reservoir in Riverside County. It also imports water supplies from northern California via the 444-mile (715 km) California Aqueduct as a contractor to the State Water Project. Metropolitan operates sixteen hydroelectric facilities, nine reservoirs, 830 miles (1,340 km) of large-scale pipes, and five water treatment plants. Four of these treatment plants are among the ten largest plants in the nation. In fact, Metropolitan is the largest distributor of treated drinking water in the United States. It serves parts of Los Angeles, Orange, San Diego, Riverside, San Bernardino and Ventura counties. The district covers the coastal and most heavily populated portions of Southern California; as well as large portions of San Diego, San Bernardino and Riverside counties are located outside of its service area.