On December 30th, 1878 the site was dubbed Fort Assiniboine, with one “n”; the fort retained that spelling until officially changed to Fort Assinniboine December 3, 1884. Between 1879 and 1903, Fort Assinniboine served as a key component of a national military strategy to secure the International Border with Canada with respect to an overall policy of intimidation and containment of Native American nations. It represents one of several open-planned post (fort) complexes constructed between 1877 and 1879 in Montana, the Dakotas, Wyoming, Nebraska, and Idaho. Fort Assinniboine’s primary function was border patrol and engagement with the Cree, Metis, Blackfeet, and Sioux. Its location between the Blackfeet reservation to the west and Fort Belknap to the east, led to interaction with the Gros Ventre and Assiniboine nations as well. While fort personnel rarely engaged in battle, the fort’s role in the United States’ military and diplomatic relationships with tribes and Canada proved crucial. The mere fact of the fort’s existence undoubtedly dissuaded, or at least caused pause to consider, possible actions by Native Americans. As Fort Assinniboine personnel were charged not only with patrol, seizure, deportation, and combat, but also protection and assistance, they effectively influenced national Indian policy and impacted the lifeways of those native populations.

The size and scale of Fort Assinniboine’s military post and 220,000-acre military reservation established it as one of the most massive in the United States. The large number of soldiers stationed there over the majority of its lifetime, and the allocation of Congressional funding for upgrades, renovation, and new construction testify to the post’s primary importance in the larger military mission of containment and border control. The district stands at a critical location, chosen to secure the northern tier, to protect settlers, and to maintain International relations by thwarting what was considered unauthorized crossing of the boundary between Canada and the United States by Native Americans, mostly the Cree and Métis.

Beginning in April 1892, one or a combination of companies from the 24th and 25th Infantries or 10th Cavalry served continuously at the fort through August 1900. Formed in 1866 after the Civil War, these regiments for black enlisted men, led by white officers, were instrumental to the United States’ military campaigns and policy enforcement in the West. Not only did the troops fully participate in the military aspects during their stay, they engaged with, and in some cases, chose to remain in the surrounding communities after their service.

With the near-containment of tribal nations in the area by the late 1890s, the purpose of the post began to change. The Spanish American War’s outbreak in 1898 initiated the transfer of companies including the 10th United States Cavalry, a unit of all African American Buffalo Soldiers commanded by Lt. “Black Jack” John J. Pershing, to military action overseas. A measurably smaller number of military personnel manned the station, but continued to conduct patrols, intercede in tribal affairs, and work with and support other forts in the region. In 1903, Congress designated Fort Assinniboine a training facility, and invested in new construction and renovation at the base. However, its remoteness and harsh winters combined with shifts in military priorities thwarted the fort’s training facility role. In 1911, the United States military abandoned Fort Assinniboine and transferred it to the Department of the Interior. After 1913, some of the fort property transitioned to state ownership as an agricultural experiment station. A large amount of its acreage was set aside for Rocky Boy’s Reservation, and additional land became Beaver Creek Park.