After the Battle of the Little Bighorn in 1876, the U.S. Army created forts in eastern Montana, including one where the north-flowing Tongue River flowed into the east-flowing Yellowstone River. The first fort was known as the Tongue River Cantonment or the Tongue River Barracks and was founded on August 27, 1876. A second, permanent fort was constructed on higher ground two miles to the west of the mouth of the Tongue and this became Fort Keogh.