The earliest Waterbury teams played in the Connecticut State League between 1884 and 1912. These teams went by several different nicknames during this period, including the Brassmen, Brass City, Indians, Pirates, Rough Riders, Authors, Invisibles, Finnegans, Champs and Spuds.
Waterbury became home to professional baseball again in 1966 when the Waterbury Giants, an affiliate of Major League Baseball's San Francisco Giants came to town. From 1966-1986 (with the exception of 1972), the Waterbury team played in the Eastern League as an affiliate of the Giants, Cleveland Indians, Pittsburgh Pirates, Los Angeles Dodgers, Oakland Athletics, Cincinnati Reds and California Angels. The team name changed every time the affiliation agreement changed hands. Waterbury did not have an Eastern League team at the start of the 1972 season. However, midway through the season, flooding in Elmira, New York made the home ballpark of the Elmira Pioneers unusable, forcing them to play their "home games" in the second half of the 1972 season in Waterbury.
The Independent Northeast League chose to place a team in Waterbury in 1997 as the Waterbury Spirit, but they folded after the 2000 season, only to be resurrected in 2003 under a new owner, relocating to Lynn, Massachusetts and becoming the North Shore Spirit.