In 1910, Foster created his own team called the Chicago American Giants. They became one of the best African-American teams in baseball history.
Foster gathered owners of the African-American teams at the Kansas City YMCA in 1920 to organize the Negro National League.
After working out the details of the new league, the owners appointed Foster as president and treasurer of the National Negro League. During this time he continued to be manager and owner of the American Giants.
Foster was elected into the Baseball Hall of Fame in 1981.