Sioux & Assiniboine Tribes and Fort Peck Reservation Timeline


Last Updated: 11 years

The largest and oldest histories of Montana Tribes are still very much oral histories and remain in the collective memories of individuals. Some of that history has been lost, but much remains vibrant within community stories and narratives that have yet to be documented. This is a brief Souix and Assiniboine Tribes and Fort Peck Reservation Timeline.


Time Immemorial Creation –Western Siouan-speaking tribal groups were located west of Lake Michigan, inhabiting a region including present-day southern Wisconsin, southeastern Minnesota, northeastern Iowa, and northern Illinois.

1600s –Assiniboines lived in northwest Ontario, Saskatchewan and eastern Alberta. (Northern and Southern Assiniboines). The Assiniboine established trade with the French and British. Assiniboine were pressured from both Chippewa and Cree. Cree had already secured weapons from traders. Assiniboine allied and intermarried with the Cree. Cree and Assiniboine pressed militarily against the Dakotas (Sioux).

1640 –References to Sioux Tribes depicted them as two groups the “Sioux of the East” and the “Sioux of the West,” being separated by the upper Mississippi River in Minnesota. The four tribes of the Sioux of the East became known as the Dakota proper, or Santee Sioux. The four tribes were Mdewakanton, Wahpekute, Sisseton, and Wahpeton. Twelve villages were identified as “Sioux of the West.” Yanktons, Yanktonais and Ti’tu’wa.

1720-1730 –Dakota secured trade with the French and moved aggressively against the Assiniboine and Cree.

1730 –Eastern Sioux abandoned their northern homelands in Minnesota and moved to the west side of the Mississippi.

1730s –Southern Assiniboine and Western Cree moved west for subsistence and in response to Dakota war pressures. The Northern Assiniboine continued their economy of fishing, waterfowl, moose and caribou.The Southern Assiniboine began to hunt buffalo. Southern Assiniboines traded with the Hidatsa and Mandan.

1750s –Southern Assiniboines acquired horses.

1777 –Founding of Hudson’s House on the lower North Fork of the Saskatchewan River. Inter-tribal conflicts developed among the Assiniboine, Gros Ventre and Cree, as each tribe desired control of the tribal trade.

1781 – 1782 –Smallpox epidemic among the Assiniboines, Gros Ventres, Blackfeet and Western Cree. This epidemic was one of the most important events to influence two-thirds of the southern Assiniboine to move south. The second motivation was trade with the Europeans and the Mandan and Hidatsa.

1800 –By this time, the Assiniboine relied heavily upon horses and had evolved to a plains economy, with bison at the center. Assiniboine tipis used a three-pole base and required twelve or more bison hides to complete the cover.

1826 –Treaty of 1826 – Assiniboine

1837 –Second major smallpox epidemic.

1851 –Fort Laramie Treaty with the Cheyenne, Arapaho, Ogallala, Brule Sioux, Crow, Shoshone, Assiniboines, Gros Ventre, Mandans, Arikaras and Minnitarees – an estimated 10,000 Indians were present. The treaty recognized vast territories for the different tribal groups and secured the right to build roads and erect forts in the tribal territories. The right to build roads through tribal lands was to accommodate travel to Oregon and California. Gold had been discovered in California in 1848.

1852 –Fort Laramie Treaty was amended.

1855 –The Judith River/Lame Bull Treaty with the Blackfeet Nation defined and common hunting grounds, and identified Assiniboine hunting rights.

1855 –Fort Stewart was built on the Missouri River near present-day Blair, Montana.

1857 –Sioux & Assiniboine battle on the Poplar River. This incident referred to a battle in which Sitting Bull prevented warriors from killing an Assiniboine boy. Eastman knew Sitting Bull and reported these words on the event: “The second incident that made him well known was his taking of a boy captive in battle with the Assiniboines. He saved this boy’s life and adopted him as his brother. Hóhay, as he was called, was devoted to Sitting Bull and helped much in later years to spread his fame.” (Eastman, Charles. Indian Heroes and Great Chieftains. Boston: Little, Brown, & Co., 1918 and Lincoln: University of Nebraska Press, 1991, p. 114) Other primary sources on this incident were related in Robert M. Utley’s book The Lance and the Shield: The Life and Times of Sitting Bull (Ballantine Books, 1994). These sources describe the incident as a battle in which people on both sides were killed.

1860 –Fort Kipp was built on the Missouri River above the mouth of the Big Muddy.

1861–Fort Poplar was built on the Missouri River near the Poplar River.

1862 –The Sioux wars began with the Santee uprising in Minnesota. Two treaties, one in 1851 and 1858, brought settlers into the rich Minnesota agricultural lands ceded by the Dakota. Trying to exist in a diminished land base, surrounded by settlements, and cheated the annuities promised by the treaties, the Dakota made the decision to go to war. The violence lasted six weeks, ending with the hanging of 39 Dakota men. Their sentence was ordered in a letter written by President Lincoln in December 1862.

1865 –The United States negotiated a treaty with Sioux bands they deem “friendly.”

1866 –The United States began negotiations with hostile Sioux over travel routes to Montana. Red Cloud declared war when the United States moves to fortify the Bozeman Trail. The campaign ended with the annihilation of Colonel Fetterman and his troops.

1868 –The Fort Buford military reserve was established from Assiniboine lands.

1868 & 1869 –Gros Ventre, Assiniboine, and River Crow were assigned to the Upper Milk River Agency.

1868 –The Fort Laramie Treaty of 1868 established the Great Sioux Reservation as the permanent homeland of the Sioux Nation and preserves the Powder River and Big Horn country as “unceded Indian territory.”

1868 –A sub-agency was built to furnish rations to the lower Assiniboine, Sioux, Gros Ventre, and River Crows. The agency was built south of the Milk River and is called Fort Browning. In keeping with President Grant’s Peace Policy, the Fort Peck Tribes were awarded to the Methodist denomination.

1870 –President Grant’s second annual message to Congress on December 5, 1870, outlined his policy on Indian Affairs: “Reform in the management of Indian affairs has received the special attention of the Administration from its inauguration to the present day. The experiment of making it a missionary work was tried with a few agencies given to the denomination of Friends, and has been found to work most advantageously. All agencies and superintendencies not so disposed of were given to officers of the Army. The act of Congress reducing the Army renders army officers ineligible for civil positions. Indian agencies being civil offices, I determined to give all the agencies to such religious denominations as had heretofore established missionaries among the Indians, and perhaps to some other denominations who would undertake the work on the same terms–i.e., as a missionary work. The societies selected are allowed to name their own agents, subject to the approval of the Executive, and are expected to watch over them and aid them as missionaries, to Christianize and civilize the Indian, and to train him in the arts of peace. The Government watches over the official acts of these agents, and requires of them as strict an accountability as if they were appointed in any other manner. I entertain the confident hope that the policy now pursued will in a few years bring all the Indians upon reservations, where they will live in houses, and have schoolhouses and churches, and will be pursuing peaceful and self-sustaining avocations, and where they may be visited by the law-abiding white man with the same impunity that he now visits the civilized white settlements. I call your special attention to the report of the Commissioner of Indian Affairs for full information on this subject.”

1871 –Fort Peck Agency was established at old Fort Peck to serve the lower Assiniboine and Sioux.

1871 –Indians attached themselves to the agency.

1872 –The United States provided aid to the Fort Peck agency.

1873 –Executive Order by President Grant established an undivided reservation for the Blackfeet, Gros Ventre, Assiniboine and Sioux. The territory covered lands north of the Missouri and Sun River. Fort Peck Agency was opened at the confluence of the Milk River and the Missouri Rivers.

1874 –President Grant’s Executive Order diminished tribal territories, moving the southern boundary north of the Sun River to the Marias.

1876 – 1877 –Sioux campaign with Sitting Bull

1876 –The Sioux were given the date of January 31, to return to the reservation from their hunting expedition or they would be considered as hostiles.

1876 –The Battle of the Little Big Horn

1877 –The agency moved to a site on the Poplar River. General Miles was stationed at Fort Peck to maintain order.

1877 –Sitting Bull fled to Canada.

1879 –Presbyterians were granted permission from the Methodists to start a mission on the reservation.

1880 –A military post was established at a point just north of Poplar. It remained until around 1893.

1881 –Chief Gall surrendered.

1881 –Sitting Bull surrendered at Fort Buford.

1883 –Starvation on the Fort Peck Indian Reservation – in part due to the extermination of buffalo.

1885 –A proposal was put forth to divide the reservation.

1886 –A treaty, establishing the confines of the Fort Peck reservation, was entered into between the Indians and the government. This reservation was created from the existing one established for multiple tribes by Grant’s Executive Order in 1874.

1887 –Railroads were built through northern Montana reservations.

1887 –An agreement was negotiated, ceding 17,500,000 acres of land to the US Government, and dividing the remaining 6,000,000 into three separate reservations – The Blackfeet, Fort Belknap and Fort Peck. This is often referred to as the Sweetgrass Hills Treaty/Agreement.

1888 –Congressional Act ratified the Sweetgrass Hills Agreement establishing the Fort Peck Reservation.

1889 –Beef rations to the Fort Peck Tribes were cut in half.

1889 –Congressional Act reduced the Fort Peck Reservation to its current size.

1896 –The federal government discontinued aid to Indian Missions.

1897 –The Catholics established a mission on Fort Peck Reservation.

1908 –Passing of the Allotment Act for Fort Peck Reservation lands.

1909 –Yankton and Assiniboine Council elected a business Committee and considered application for enrollment.

1913 –1,348,408 acres of reservation lands were deemed “surplus,” after tribal allotments were made. This land was opened up for homestead entry.

1927 –The Fort Peck Tribes developed a tribal Constitution.

1950s –Oil was discovered and there was a subsequent oil boom.

1960 –Fort Peck Tribes revised their Constitution and By-Laws.

1978 –Fort Peck Community College was chartered.

Buy Assiniboine T-shirt1980s –The second oil boom on the Fort Peck Reservation

2008 –The Fort Peck Tribes held a constitutional convention.