Fort Halleck, named in honor of Gen. Henry W. Halleck, one of the noted Union .generals in the Civil war, was established on July 20, 1862. It was located near the foot of the Medicine Bow Mountains and was for a time the most important military post in the Rocky Mountain region, being the center of the Indian warfare of that period. In the spring of 1863, when Capt. J. L. Humfreville of the Eleventh Ohio Cavalry was in command of the post, the troops worked both east and west from the fort, guarding mail coaches and emigrant trains, and saw hard service. Early in 1865, when the Indians began their raids on the Overland stations, the garrison at Fort Halleck was increased. A year later the seat of Indian warfare had shifted to the valleys of the Big Horn and Powder rivers, and on July 4, 1866, Fort Halleck was abandoned.
Source: History of Wyoming, Volume 1, by I. S. Bartlett, Chicago, The S. J. Clarke Publishing Company, 1918