McLaughlin obtained his United States citizenship in 1865. In 1871 he was hired by the commanding officer of Fort Totten, North Dakota, as a blacksmith and general overseer at the Devils Lake Indian Agency; the U.S. Army outpost was in what was then called the Dakota Territory. While there, he studied to become a United States Indian agent; at the time Indian affairs were supervised as part of the Department of the Army. Army officers noted that he established good relations with the Lakota. In 1876 he was appointed as agent of the Devils Lake Agency in present-day North Dakota, the reservation for a Sisseton Wahpeton tribe of the Dakota people.