The Gros Ventre are historically an Algonquian-speaking Native American tribe. They are known as A’ani, Haaninin, and Atsina, and they call themselves “AH-AH-NE-NIN” meaning the White Clay People. They believed that they were made from the White Clay that is found along the river bottoms in Gros Ventre country. Early French fur trappers and traders named this tribe “Gros Ventre” because other tribes in the area referred to them as “The Water Falls People.” The sign for water fall is the passing of the hands over the stomach and the French thought the Indians were saying big belly so they called them “Gros Ventre” meaning “big belly” in the French language.
The Gros Ventre are believed to have lived in the western Great Lakes region 3000 years ago, where they lived an agrarian lifestyle, cultivating maize. With the ancestors of the Arapaho, they formed a single, large Algonquian-speaking people who lived along the Red River valley in northern present-day Minnesota and in Manitoba, Canada. They were closely associated with the ancestors of the Cheyenne.
In the early 18th century, this large tribe split into two, forming the Gros Ventre and the Arapaho. These tribes and the Cheyenne, were among the last tribes to migrate into Montana. However, the Arapaho later moved on to the Wyoming and Colorado area.
In the mid-18th century, the Gros Ventre acquired horses and at this time experienced their first encounter the whiteman in approximately 1754, near the Saskatchewan River. The resulting exposure to smallpox severely reduced their numbers
In the 19th century, the Gros Ventre joined the Blackfeet Confederacy. After allying with the Blackfeet, the Gros Ventre moved to north-central Montana and southern Canada.
In 1868, the United States government established a trading post called Fort Browning near the mouth of Peoples Creek on the Milk River. While this trading post was originally built for the Gros Ventre and Assiniboine tribes, it was built on a favorite hunting ground of the Sioux Indians, and it was abandoned, as a result in 1871. After the abandonment of Fort Browning, the government built the on the south side of the Milk River, about one mile southwest of the present town of Chinook, Montana.
In 1876, Fort Browning was discontinued and the Gros Ventre and Assiniboine people who were receiving annuities at the post were instructed to go to the agency at Fort Peck and Wolf Point.
The Assiniboine did not object to going to Wolf Point. The Gros Ventre, however, refused make the move knowing they would come into contact with the Sioux, with whom they could not ride together in peace. The Gros Ventre forfeited their annuities rather than make the move to Fort Peck.
In 1878, the Fort Belknap Agency was re-established, and the Gros Ventre, and remaining Assiniboine were again allowed to receive supplies at Fort Belknap. Then in 1888. the Fort Belknap Indian Reservation was established, named for William W. Belknap, who was Secretary of War at that time.
By an act of Congress on May 1, 1888, (Stat., L., XXV, 113), the Blackfeet, Gros Ventre, and Assiniboine tribes ceded 17,500,000 acres of their joint reservation and agreed to live upon three smaller reservations. These are now known as the Blackfoot Confederacy, the Fort Peck Indian Reservation and the Fort Belknap Indian Reservation. By 1904 there were only 535 A’ani tribe members remaining. Since then, the tribe has revived, with a substantial increase in population.
There are currently over 8,000 enrolled members in the Fort Belknap Indian Community, which includes the Assiniboine people, who were historical enemies of the Gros Ventre.