Fort Abraham Lincoln log scouts' quarters. Water was supplied to the fort by being hauled from Missouri River in wagons, while wood was supplied by contract. By 1873, the 7th Cavalry moved into the fort to ensure the expansion of the Northern Pacific Railway. The first post commander of the expanded fort was Lieutenant Colonel George A. Custer, who held the position until his death in 1876. In 1876, the Army departed from here as part of the Great Sioux War of 1876-77, resulting in Custer's defeat at the Battle of the Little Bighorn, where they were to push the non-treaty Indians back
George Armstrong Custer agencies (reservations) or be considered "hostile". At that time the 7th Cavalry's regimental commander, Colonel Samuel D. Sturgis, was on detached duty as the Superintendent of Mounted Recruiting Service and in command of the Cavalry Depot in St. Louis, Missouri, which left Lieutenant Colonel Custer in command of the regiment. Custer and the 7th Cavalry departed from Fort Abraham Lincoln on May 17, 1876, part of a larger army force planning to round up remaining free Indians. Meanwhile, in the spring and summer of 1876, the Hunkpapa Lakota holy man Sitting Bull had called together the largest ever gathering of