New York-born Boss was one of the screen's first child stars. He was already a stage veteran when he made his screen debut in Thanhouser's The Actor's Children (1910). He appeared on Broadway opposite Adeline Genée in The Silver Star. Later he became one of Edison Studios's most popular players, but the studio constantly had to battle rumors questioning his true age. Boss's popularity waned in the late 1910s and he later worked as a prop man.