Green River is a city in Sweetwater County, Wyoming, United States. The population was 11,808 at the 2000 census. It is the county seat of Sweetwater County. Its importance as part of the Dakota Territory was enhanced when it was made a division point for the Union Pacific railway in 1868, the year of its incorporation. The city is also known as being one of the first in the United States to ban door-to-door solicitation; see Green River Ordinance.