The greatest first baseman in Negro League history, Leonard teamed with Josh Gibson over a 10 year period to give the Homestead Grays a 1-2 hitting punch comparable to Ruth and Gehrig and lead them to nine consecutive Negro Natoinal League pennants between 1937 and 1946. They were known as the "Thunder Twins."

A left handed batter who hit for average and distance, Leonard averaged .336 with 29 home runs per year over his 17 year career. Leonard also played year round, playing in Cuba, Puerto Rico, Mexico, and Venezuela. He was elected to Cooperstown's Hall of Fame in 1972.