In the 1855 Treaty of Hellgate, leaders of the Salish ("Flathead"), Pend d'Oreille, and Kootenai tribes ceded to the United States most of their lands west of the Continental Divide while reserving certain areas, including this 13-million-acre reservation, for their exclusive use and benefit, and also retaining the right to hunt, gather, fish, and pasture their animals on open and unclaimed portions of their ceded lands. In 1904, Congress violated the treaty's guarantee of the reservation as a sovereign homeland by passing the Flathead Allotment Act, part of a broader effort to force Indian people to abandon traditional ways of life by dismantling tribal ownership of land. Between 1904 and 1908, the government surveyed the Flathead Reservation and allotted individual parcels to Indian heads of households, then declared most of the remaining land surplus and opened it to non-Indian homesteaders. During the 1910s, aided by construction of the massive Flathead Indian Irrigation Project, non-Indians took control of most of the best lands and the reservation economy. In 1934, Congress ended allotment policy with the Indian Reorganization Act, and the Confederated Salish and Kootenai Tribes became the first in the nation to adopt a new constitution under its terms, then gradually rebuilt their sovereignty and developed one of the most accomplished tribal governments in the U.S.