Green River is a city in and the county seat of Sweetwater County, Wyoming, United States, in the southwestern part of the state. The population was 11,808 at the 2000 census. The city is known as being one of the first in the United States to ban door-to-door solicitation; see Green River Ordinance. The Mayor of Green River is Henry Castillon, who was elected in November 2006 and won re-election in 2010. Green River was incorporated in 1868 in what was then the Dakota Territory. The city was the starting point from which John Wesley Powell started his famous expeditions of the Green River, the Colorado River, and the Grand Canyon in the late 1800s.