Portions of the High Plains were not settled until the early 20th century because water was needed for irrigation. Responding to pressure for Western settlement, Congress created the Reclamation Service in 1902. Its purpose was to develop water resources by making possible cultivation of what was considered desert wasteland. One effort was the Riverton Project. Located in the Wind River Basin it was undertaken by the Bureau of Reclamation in 1920.
The Midvale Irrigation District of the Riverton Project involves 73,000 acres, three dams — Bull Lake Dam to the south and Diversion Dam and Pilot Butte Dam to the east, 100 miles of canals and 300 miles of laterals. Diversion Dam, completed in 1923, diverts water from the Wind River to the Wyoming Canal. It is noteworthy as the first dam in the nation with a road incorporated into its structure and the first to contain a fish ladder.
Historian T.A. Larson describes the Riverton irrigation project as "a perennial object lesson in the formidable difficulties inherent in large-scale reclamation projects in the West." Initially posing financial and engineering problems, it came to involve legal and political issues. During the rise of Native American self determination the Arapaho and Shoshone tribes exercised their right to Wind River water, granted by an 1868 treaty. Court battles
were fought over water used to irrigate land opened to homesteading by Congress in 1905. The struggle highlights the importance of water to the West.