Trumbull continued to oversee his business interests. He also served as a Delegate to the Republican National Convention from Connecticut in 1920 as Alternate. Organizer and president, Trumbull Electric Manufacturing Co.; board chairman, Colonial Air Transport, Inc.; director and treasurer, Plainville Realty Co.; president, Plainville Trust Co.; director, Connecticut Light & Power Co.; delegate to Republican National Convention from Connecticut, 1920 (alternate), 1924, 1928, 1932, and 1936. He stayed active as vice president of the Connecticut Humane Society and the Connecticut Historical Society.