Foster, considered by historians to have been perhaps the best African-American pitcher of the first decade of the 1900s, also founded and managed the Chicago American Giants, one of the most successful black baseball teams of the pre-integration era.

[6] Foster started his professional career with the Waco Yellow Jackets, an independent black team, in 1897 and played for the Hot Springs Arlingtons in 1901.

[8][9][10] A newspaper story in the Trenton (NJ) Times from July 26, 1904, contains the earliest known example of Foster being referred to as "Rube," indicating that the supposed meeting with Waddell must have taken place earlier than that.

Legend has it that John McGraw, manager of the New York Giants, hired Foster to teach the young Christy Mathewson the "fadeaway", or screwball, though historians have cast doubt on this story.

In a rematch with Foster's old team, the Cuban X-Giants, he won two games and batted .400 in leading the Philadelphia Giants to the black championship.

Under his leadership, the Lelands won 110 games (including 48 straight) and lost only ten, and took the Chicago City League pennant.

Foster suffered a broken leg in July 1909, but rushed himself back into the lineup in time for an October exhibition series against the Chicago Cubs.

By 1915, Foster's first serious rival in the midwest had emerged: C. I. Taylor's Indianapolis ABCs, who claimed the western championship after defeating the American Giants four games to none in July.

The continued wrangling led to calls for a black baseball league to be formed, but Foster, Taylor, and the other major clubs in the midwest were unable to come to any agreement.

He asserted control over every aspect of the game, and set a high standard for personal conduct, appearance, and professionalism among his players.

Given Schorling Park's huge dimensions, Foster developed a style of play that emphasized speed, bunting, place hitting, power pitching, and defense.

He was also considered a great teacher, and many of his players themselves eventually became managers, including Pete Hill, Bruce Petway, Bingo DeMoss, Dave Malarcher, Sam Crawford, Poindexter Williams, and many others.

In 1920, Foster, Taylor, and the owners of six other midwestern clubs met in the spring to form a professional baseball circuit for African-American teams.

After two years of finishing behind the Monarchs, Foster "cleaned house" in spring 1925, releasing several veterans (including Lyons and pitchers Dick Whitworth and Tom Williams).

Suffering from serious delusions, including one where he believed he was about to receive a call to pitch in the World Series, he was institutionalized midway through the 1926 season at an asylum in Kankakee, Illinois.

Postal Service announced that it planned to issue a pair of postage stamps in June honoring Negro leagues Baseball.

[19] On July 17, 2010, the Postal Service issued a se-tenant pair of 44-cent, first-class, U.S. commemorative postage stamps, to honor the all-black professional baseball leagues that operated from 1920 to about 1960.

[20] The Negro Leagues Baseball Museum hosts the annual Andrew "Rube" Foster Lecture, in September.

[21] On November 10, 2021, the United States Mint announced the designs for the 2022 Negro Leagues Centennial Commemorative coins, with Foster featured on the $5 gold half eagle.