At first, the Indians actually had the advantage because their arrows could be fired more rapidly than a muzzle-loading rifle. The invention of the Colt .45 revolver (the six-shooter by Samuel Colt) and Winchester repeating rifle changed this.
Notably, one-fifth of the U.S. Army out West was black, the "Buffalo Soldiers" as the Indians called them.
Receding Native Population
Violence out West began just before the Civil War ended.
Col. J.M. Chivington's troops circled then killed 400 Indians who thought they'd been given immunity. This was the infamous Sand Creek Massacre (1864).
Two years later, the Indians struck revenge in the Fetterman Massacre. The Sioux sought to stop the Bozeman Trail to Montana's gold and killed Capt. William J. Fetterman and his 81 soldiers.
These two tic-for-tac massacres set the stage for terrible Indian-white relations and started the Indian wars.
Just after Fetterman, the Treaty of Fort Laramie (1868) was made between the federal government and the Sioux. The government gave up on the Bozeman Trail and the huge Sioux reservation was established. The treaty looked promising but was short-lived.
Six years later, in 1874, gold was discovered in the Black Hills of South Dakota (on the Sioux reservation) when Col. William Armstrong Custer led a "geological" expedition into the Black Hills.
The Battle of Little Bighorn (1876) (AKA "Custer's Last Stand") followed.
Led by Crazy Horse and Sitting Bull, some Sioux stubbornly refused to go to the reservation.
Custer led about 400 cavalry against Crazy Horse who was labeled as a "hostile" Indian. Custer faced some 10,000 Indians, about 2,500 warriors. All 200+ or so of Custer's detachment were killed, including Custer himself, "Chief Yellow Hair."
The Little Bighorn battle