In 1910, Foster, captain of the Chicago Leland Giants, wrested legal control of the name "Leland Giants" away from the team's owner, Frank Leland. That season, featuring Hall of Fame shortstop John Henry Lloyd, outfielder Pete Hill, second baseman Grant Johnson, catcher Bruce Petway, and pitcher Frank Wickware, the Leland Giants reportedly won 123 games while losing only six. In 1911, Foster renamed the club the "American Giants."
Playing in spacious Schorling Park (formerly the home field of the American League's Chicago White Sox), Foster's club relied on fielding, pitching, speed, and "inside baseball" to dominate the young Negro National League (NNL), winning championships in 1920, 1921, and 1922. When the Kansas City Monarchs displaced the American Giants beginning in 1923, Foster tried rebuilding; but by 1926 his health (physical and mental) was failing, and his protegé Dave Malarcher took over on-field management of the team. Malarcher followed Foster's pattern, emphasizing pitching and defense, and led the American Giants back to the pinnacle of the Negro Leagues, winning pennants in 1926 and 1927. Both seasons also saw the American Giants defeat the Bacharach Giants of Atlantic City, champions of the Eastern Colored League, in the Negro League World Series.
The NNL collapsed in 1931 and in 1932 the team won the Negro Southern League pennant as Cole's American Giants. The next season the American Giants joined the new Negro National League, narrowly losing the pennant to the Pittsburgh Crawfords in a controversial decision by league president Gus Greenlee (owner of the Crawfords). In 1934, the American Giants won the NNL's second-half title, then fell to the Philadelphia Stars in a seven-game playoff for the championship. In 1937, after a year spent playing as an independent club, the American Giants became a charter member of yet another circuit, the Negro American League.
Ted "Double Duty" Radcliffe was appointed manager in 1950. The team’s owner, Dr. J.B. Martin, was concerned about black players joining Major League teams so he instructed Radcliffe to sign white players. Radcliffe recruited at least five young white players (Lou Chirban, Lou Clarizio, Al Dubetts, Frank Dyall and Stanley Miarka).