Professional baseball in Louisville goes all the way back to 1876 and the Louisville Grays, charter members of the National League. They only lasted two seasons, dissolving after several key players were found to be mixed up with gamblers.
In 1882, the Eclipse began playing in the American Association (AA) changing their name to the Colonels in 1885. After the AA folded at the conclusion of the 1891 season, the Colonels joined the National League.
In 1887, Louisville also fielded a team in the National Colored Baseball League for that circuit's two-week existence.
For the 1900 season, the National League contacted by four teams, dismissing Cleveland, Baltimore, Louisville, and Washington. Louisville became the only city to lose a major league baseball team and not get another one until Montreal bade farewell to the Expos in 2004 as that team moved to Washington, D.C.
However, the Colonels joined the Western League which had just been renamed the American League (AL), for the 1900 season. A minor league at that time, the AL declared major league status for 1901. However, the Colonels were not part of the new 8-team circuit and wound up in a different minor league, the American Association where they stayed until that league folded in 1962.
During that time, a number of Negro League teams called Louisville home starting with the independent Louisville White Sox in 1930, who joined the Negro National League in 1931, folding at the end of that season.
The Louisville Black Caps were established in the Negro Southern League in 1932, playing one season in that circuit. Two more independent teams followed, the Red Caps in 1933 and the Black Colonels in 1939. In 1949, the Cleveland Buckeyes moved to Louisville but moved back to Northern Ohio in 1950.
In 1968, the Toronto Maple Leafs of the International League moved to Louisville and were renamed the Colonels. They stayed until 1972 having been forced to move when Fairgrounds Stadium was reconfigured for football only. The Colonels headed to Pawtucket, Rhode Island to become the Red Sox.
That left Louisville without a baseball team until the Springfield Redbirds, of the American Association (which had been restarted in 1968), moved to town in 1982. That team started in Tulsa in 1905 as the Oilers.
The team moved into old Fairgrounds Stadium which had just been renovated again, this time being returned to a baseball-friendly configuration.
In Louisville, the Redbirds, the top farm club of the St. Louis Cardinals, were a huge a hit, breaking all minor league attendance records in their first season. In 1983, they became the first minor league team to draw over a million fans in one season. This led to speculation that Louisville might be a candidate for an MLB expansion franchise. Indeed, former Cincinnati Reds great and then politician Jim Bunning initiated efforts to bring big league baseball back to the city.
In 1998, the team became an affiliate of the Milwaukee Brewers while the Cardinals established a new Redbirds franchise in Memphis playing in the Pacific Coast League. For a year the two teams used the Redbirds name. In 1999, Louisville adopted the name RiverBats, shortening it to simply Bats in 2002.
In 2000, the team moved into Louisville Slugger Field and became the Reds’ top farm team and continue to be one of the minors top drawing clubs.