The Platte River (or Nebraska River) is a river system in the Great Plains of the United States and is a tributary to the Missouri River. The Platte River is composed of two affluents, the South Platte River and the North Platte River. The Platte River proper forms at the junction of these two tributaries near North Platte, Nebraska and meanders east through Nebraska to its outlet into the Missouri River at Plattsmouth, Nebraska, just south of Omaha. Including the North Platte, the Platte River stretches over 900 miles, with a drainage basin of 90,000 square miles.
The South Platte rises near Fairplay, Colorado, in the South Park Basin of the Rocky Mountains, and plummets steeply through Eleven Mile Canyon before hitting the plains near Denver. It continues north through flat Colorado plains before entering Nebraska near Julesburg.
The North Platte originates in the North Park area near Walden, Colorado, whence it crosses nearly due north into Wyoming. The river turns east near Casper, Wyoming, then south east to meet the Laramie River before crossing into Nebraska, passing between the cities of Scottsbluff and Gering.
The first European to discover the Platte in 1714 was Étienne de Veniard, sieur de Bourgmont, who named it the Nebraskier, an Oto word meaning "flat water". The French word for flat, Platte, was later applied. The river provided valuable transportation for the French trade in furs with the Pawnee and Oto native peoples.
The Platte lay in a gray area between Spanish and French claims in the Great Plains. Joseph Naranjo, a black explorer, had also encountered the Platte, and later guided the Villasur expedition there to stop French expansion. Theirs was the deepest penetration of Spanish exploration into the central prairies.
Ceded to the United States in the Louisiana Purchase, the Platte was explored and mapped by Major Stephen H. Long in 1820. The Platte was used by American trappers, and played an important role in westward expansion during the 19th century. It provided fresh water, game, and a clear path westward for the pioneers. Both the Oregon Trail and the Mormon Trail followed the Platte (and the North Platte). Today, Interstate Highway 80 parallels the Platte (and the North Platte) through most of Nebraska.
On the plains, the river is wide and shallow, with a broad wetlands border. The central Platte River valley is an important stopover for migratory water birds, such as the Whooping Crane and Sandhill Crane, in their yearly traversal of the Central Flyway.