Fort Fetterman was established as a military post in July of 1867. It was located on the North Platte River at the crossroads of the Bozeman Trail and the earlier overland trails. After the abandonment of Forts Reno, Phil Kearny, and C. F. Smith in 1868, Fort Fetterman became the primary protective establishment in the heart of hostile Indian country. Its strategic location made it a supply base, a headquarters and a marshaling point for several major military expeditions during the final ''Indian Wars'' on the Northern Plains. The post was named in honor of Bvt. Lt. Colonel William J. Fetterman, an infantry captain who, with his whole command of eighty-one, was killed in a fight with Indians near Fort Phil Kearny, December 21, 1866.
Major William McEnery Dye with companies A., C., H., and I. of the Fourth Infantry began construction in July, 1867, and Brigadier General H. W. Wessells became first commanding officer in November of the same year. Quartered in temporary dwellings the first winter proved difficult for the garrison. The following year these dwellings were replaced by more substantial structures of adobe, wood and stone. The development of the post continued until 1870 when it became well-established and destined to play a conspicuous part in United States military and Indian affairs for the next few years.
In 1876 it became the base for three of General George Crook's Powder River Expeditions. One expedition culminated in the ''Battle of the Rose Bud'' in which Crook came to a stand-off with his Sioux and Cheyenne opponents. These and other military actions brought the inevitable end to hostile Indian conflicts on the Plains. The role of Fort Fetterman in breaking the back of the Indian resistance also spelled the Fort's eventual doom. With the hostiles confined to reservations the post had outlived its usefulness. Military abandonment came in 1882. The Fort fell into a state of decay in the 1880s and most of the buildings were sold, dismantled or moved to other locations and the site was quietly taken over by local ranching interests. The site of Fort Fetterman was purchased by the State of Wyoming in 1962 and is open to the public as Fort Fetterman Historic Site.