What caused the Sioux war of 1876?

The Sioux War of 1876 was primarily caused by the U.S. government's desire to expand westward and the discovery of gold in the Black Hills, which were sacred to the Sioux. Following the 1868 Treaty of Fort Laramie, which recognized Sioux territory, the influx of miners and settlers into the area led to tensions and violations of the treaty. This culminated in conflicts between the U.S. military and the Sioux, particularly after the government attempted to force the Sioux onto reservations. The war is most famously marked by the Battle of Little Bighorn, where General Custer's forces were decisively defeated.