The St. Louis Cardinals, a professional baseball franchise based in St. Louis, Missouri, compete in the National League (NL) of Major League Baseball (MLB). As the game of baseball garnered interest in the United States in the 19th century, professional baseball in St. Louis became rooted chiefly in one disestablished Major League club – named the , the same as the Cardinals' earliest name – which is loosely connected, but does not fall within the scope of, today's Cardinals. The Brown Stockings became St. Louis' first fully professional baseball club when they gained accession in the National Association (NA) in 1875. However, the NA folded after that season. That winter, with five other former NA teams, St. Louis established a new, eight-team league called the National League (NL) and began play the next season. Despite early success, Brown Stocking players were found to be connected to game fixing scandals, which forced bankruptcy and the club's expulsion from the NL. This scandal also abrogated their professional status but some members maintained play as a semi-professional team, primarily operated by outfielder Ned Cuthbert, until 1881.
With interest in reviving professional baseball in St. Louis steadily growing, grocery and brewery tycoon Chris von der Ahe observed with fascination the team playing near his store and beer garden garnered large crowds. He purchased the club in 1881, and – together with other club owners (who also happened to beer magnates) interested in creating professional league that could rival the National League – made it a charter member of the American Association in , bringing professional baseball back to the Gateway City. This Brown Stockings club became St. Louis' Major League mainstay, now competing as the Cardinals. During their time in the AA, the Cardinals established the first St. Louis professional sports dynasty, finishing with best overall record in the league each year from 1885 to 1888 and the best all-time record in that league's history. They also took their first interleague championship (a precursor to the World Series), finishing off their rivals, the – now the Chicago Cubs – in the 1886 World Series.