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The Sweetwater River is a tributary of the North Platte River, approximately 150 mi (241 km) long, in the U.S. state of Wyoming. It rises in southwestern Fremont County, at the continental divide near South Pass, on the southern end of the Wind River Range. It flows ENE along the north side of the Antelope Hills, then ESE, through Fremont County, past Jeffrey City, between the Granite Mountains to the north and the Green Mountains to the south, through cattle-raising areas. In southern Natrona County, it passes Devil's Gate and Independence Rock, and empties into the North Platte as the Sweetwater arm of Pathfinder Reservoir.
The valley of the river historically provided the route of several westward migration trails, including the Oregon Trail, California Trail, and Mormon Trail, allowing access to South Pass from the plateau area of southeastern Wyoming.