Early lifeBorn in Rocky Mount, North Carolina, Leonard left school at the age of 14 because no high school education was available for blacks in his hometown. He worked in a textile mill and as a shoeshine boy at a railroad station, the latter being typical of the economic situation for many African Americans at that time.
Negro league careerHe began his Negro league career in 1933 with the Brooklyn Royal Giants, then moved to the legendary Homestead Grays in 1934, the team he played for until his retirement in 1950. The Grays of the late 1930s through the mid-1940s are considered one of the greatest teams of any race ever assembled. Leonard batted fourth in their lineup behind Josh Gibson. Since Gibson was known as the "Black Babe Ruth" and Leonard was a first baseman, Buck Leonard was inevitably called the "Black Lou Gehrig." Together, the pair was colloquially known as the "Thunder Twins" or "Dynamite Twins". From 1937 to 1945 the Grays won 9 consecutive Negro National League championships. Leonard led the Negro leagues in batting average in 1948 with a mark of .395, and usually either led the league in home runs or finished second in homers to teammate Gibson.
In 1952, Leonard was offered a major league contract, but he believed that at age 45 he was too old and might embarrass himself and hurt the cause of integration. He may well have underestimated his own longevity, however, since he batted .333 in 10 games in the Class B Piedmont League the following year, and played in Mexico through 1955, where the level of play was very high.
Later lifeAfter retiring permanently as a player in 1955, Leonard worked as a truant officer, a physical education instructor, and the vice-president of a minor league team in his birthplace of Rocky Mount, a team of which he was also a board member. He was elected to the Baseball Hall of Fame in 1972 along with Josh Gibson.
In 1994, the Major League All-Star Game was held in Pittsburgh, hometown of the Grays, and the 88-year-old Leonard was named an Honorary Captain. He appeared wearing a model of a Grays uniform. He was one of Negro league baseball's foremost ambassadors until his death at age 90 in Rocky Mount.
In 1999, he ranked Number 47 on The Sporting News' list of the 100 Greatest Baseball Players, one of five players so honored who played all or most of their careers in the Negro leagues, and was nominated as a finalist for the Major League Baseball All-Century Team.
According to Negro league statistics compiled in a project sponsored by the National Baseball Hall of Fame, Leonard's career batting average was .320 and his slugging percentage was .527. In 1,472 recorded at bats, he had 471 hits, 60 home runs, 73 doubles, and 26 triples, drew 257 walks, and scored 352 runs while driving in 275.