 He moved to Fort Pierre, South Dakota in 1848 to work as a trapper.He was a trader at Fort Berthold in the Dakota Territory and was for a time married to an Indian woman, the sister of a warrior named Whistling Bear.Gerard was hired by Lieutenant Colonel Custer to serve at Fort Abraham Lincoln as an interpreter for his Arikara "Ree" scouts, as he was very familiar with the language from his years as a trader.