The name Fort Peck is associated with Col. Campbell K. Peck, the partner of Elias H. Durfee in the Leavenworth, Kansas trading firm of Durfee and Peck. In 1867, company employee Abe Farwell constructed the Fort Peck trading post along the Missouri River, which enjoyed a virtual monopoly in trade with the Sioux and Assiniboine people. After its short life as a trading post, Fort Peck served as an Indian agency from 1873 until 1878. At that time, the agency was moved to its current location at Poplar. Fort Peck had a post office from 1879 to 1881.