Rocky Boy’s Indian Reservation in north central Montana was established by Executive Order on September 7, 1916 as a homeland for a band of the Chippewa people led by Stone Man (also known as Rocky Boy) and a band of Cree people lead by Little Bear. Despite including drainages for Big Sandy Creek and Beaver Creek the land was arid and lacked adequate water rights to support the irrigation necessary for self-sufficiency. The Reservation grew in size as the United States purchased additional land for the Chippewa Cree Tribe, but the new land was largely of poor quality; water remained inadequate and water rights were not actively asserted by the United States in its role as trustee.
The Winter's Doctrine (also known as the reserved rights doctrine), articulated by the United States Supreme Court in the case of Winters v. United States in 1908, was created to ensure that Indian lands and other lands reserved by the federal government for particular purposes would have adequate water to fulfill those purposes. However, the amount of the entitlement is uncertain until it is quantified by judicial decision or by a settlement agreement. In 1979 Montana passed Senate Bill 76 which (among other things) established the Montana Reserved Water Rights Compact Commission. The Compact Commission is responsible for negotiating on behalf of the state with federal and tribal entities to quantify the federal and tribal reserved water rights. In 1997 the Chippewa Cree Tribe and the State of Montana agreed to a water rights compact between the two governments which quantified the Tribe’s water rights and established a joint Tribe/State water administration system. On December 9, 1999, the Chippewa Cree Tribe of the Rocky Boy's Reservation Indian Reserved Water Rights Settlement Act became Public Law No: 106-163. In 2002, a Montana water court decree approved the water rights of the Chippewa Cree Tribe.
From the guide to the Chippewa Cree Tribe of the Rocky Boy's Reservation Water Resources Department water rights settlement records, 1832-2002, (University of Montana-Missoula Maureen and Mike Mansfield Library Archives and Special Collections)