Cumberland Posey began his career in 1911 playing outfield for the Homestead Grays, a local black team in his Pennsylvania hometown. He soon became the squad's driving force as they dominated semi-pro ball in the Pittsburgh area. By the late 1930s the Grays were at the top of the Negro Leagues with nine straight pennant wins.
Posey was also a League officer; he served 13 years as the first black member of the Homestead school board; and he wrote an outspoken sports column for the African American weekly, the Pittsburgh Courier. He was regarded as one of the best black basketball players in the East; he was the organizer of a team that held the consensus national black championship five years running. Ten years after his induction into the National Baseball Hall of Fame, he became a member of the Naismith Memorial Basketball Hall of Fame—one of only two athletes to be honored by two pro sports halls.