The Gros Ventre (US: /ˈɡroʊvɒnt/ GROH-vont, French: [ɡʁo vɑ̃tʁ]; meaning "big belly"), also known as the A'aninin, Atsina,[5] or White Clay,[6] are a historically Algonquian-speaking Native American tribe located in northcentral Montana.

[8] With the ancestors of the Arapaho, they formed a single Algonquian-speaking people who lived along the Red River Valley in present-day Minnesota and North Dakota.

[8] In Ojibwa oral history they are known as the "men of the olden time" that occupied the lands surrounding the head waters of the Mississippi River.

[citation needed] In the early 18th century, the combined tribe came under pressure from the Ojibwe, and started a migration to the upper Missouri River Valley.

Along with the naturalist painter Karl Bodmer, the Europeans painted portraits and recorded their meeting with the Gros Ventre, near the Missouri River in Montana.

The Gros Ventres signed the treaty as part of the Blackfoot Confederacy, whose territory near the Three Fork area became a common hunting ground for the combined peoples.

A common hunting ground north of the Missouri River on the Fort Peck Indian Reservation included the Assiniboine and Sioux.

[citation needed] In 1868, the United States government established a trading post called Fort Browning near the mouth of Peoples Creek on the Milk River.

This trading post was built for the Gros Ventres and Assiniboines, but because it was on a favorite hunting ground of the Sioux, it was abandoned in 1871.

[citation needed] The government then built Fort Belknap, which was established on the south side of the Milk River, about one mile southwest of the present town site of Harlem, Montana.

White Eagle, "the last major Chief of the Gros Ventre people", died "at the mouth of the Judith River" on February 9, 1881.

[citation needed] In March 2012, 63 American bison from Yellowstone National Park were transferred to prairie on the Fort Peck Indian Reservation, to be released to a 2,100-acre game preserve 25 miles north of Poplar.