https://en.wikipedia.org/wiki/Battle_of_the_Little_Bighorn

The 1876 Battle of the Little Bighorn, commonly referred to as Custer’s Last Stand and known to the Lakota and other Plains Indians as the Battle of the Greasy Grass, was an armed engagement between combined forces of the Lakota Sioux, Northern Cheyenne, and Arapaho tribes and the 7th Cavalry Regiment of the United States Army. It took place on June 25–26, 1876, along the Little Bighorn River in the Crow Indian Reservation in southeastern Montana Territory. The battle, which resulted in the defeat of U.S. forces, was the most significant action of the Great Sioux War of 1876.