The Platte River originates in the state of Nebraska and is about 310 miles – 500 km – long. Measured to its farthest source via its tributary the North Platte River, it flows for over 1,050 miles – 1,690 km. The Platte is a tributary of the Missouri and Mississippi Rivers which flows to the Gulf of Mexico.
River Valley Trails played an important role in the westward expansion of the United States, providing the route for several major emigrant trails, including the Oregon, California, Mormon and Bozeman Trails. The French were the first Europeans to reach the Platte. At Casper, Wyoming the trails left the North Platte valley and followed the Sweetwater River valley and other river valleys going further west.