Listed below are the Major League Baseball teams with the worst season won-lost records, as determined by win percentage (.300 or less), minimum 120 games played.
Season records
The following teams finished the season with a .300 winning percentage or lower.
Legend
NL = National League
AL = American League
AA = American Association
PL = Players' League
1886–1900
Modern era (1901–present)
1898 St. Louis Browns and 1899 Cleveland Spiders
The 1899 Cleveland Spiders own the worst single-season record of all time (minimum 120 games) and for all eras, finishing at 20–134 (.130 percentage) in the final year of the National League's 12-team era in the 1890s; for comparison, this projects to 21–141 under the current 162-game schedule, and Pythagorean expectation based on the Spiders' results and the current 162-game schedule predicts a record of 24–138.
The Spiders had reasonable success in the 1890s, with seven straight winning seasons from 1892 to 1898 and a Temple Cup victory in 1895, while the once four-time American Association champion St. Louis Browns had fallen to 29–102 in 1897 (11–61 on the road) and to 39–111 (19–67 on the road) in 1898. The Spiders ownership, the Robison brothers, bought the Browns in time for the 1899 season, creating a conflict-of-interest situation which was later outlawed, and on the eve of the season, traded almost all of Cleveland's star players to St. Louis for very little in return, with respectable results for St. Louis and disastrous results for Cleveland.
The 1899 Spiders set the major league record for most consecutive losses in a season (24, from July 26 to September 16), and had six losing streaks of 10 games or more. The Spiders lost 40 of their last 41 games, finishing 84 games behind the 1899 National League champion Brooklyn Superbas and 35 games behind the second-last-placed Washington Senators. They also lost 27 games in September, a record for the most games lost in a month until the 1909 Washington Senators went 5–29 in July.
Due to paltry attendances, the Spiders played 112 games on the road, finishing with a road record of 11–101 (the 101 road losses is a record which is unbreakable under the current MLB scheduling rules, which allow a maximum of 81 road games).
The 1899 Browns, renamed the "Perfectos" and staffed with all the best players from the 1898 Spiders (six of the Spiders' eight starting position players, and four starting pitchers, including the great Cy Young) improved by 44½ games, from 39–111 to 84–67. However, all St. Louis ultimately did was trade places with Cleveland in the standings. The Browns/Perfectos were renamed the St. Louis Cardinals in 1900, and are unrelated to the American League St. Louis Browns that adopted the discarded nickname and also appear on this list.
After the 1899 season, the National League contracted from twelve to eight clubs for the 1900 season, with the Spiders, the original Baltimore Orioles, Louisville Colonels (Louisville has not had another major league team since), and the original Washington Senators folding operations. Baltimore had also been stripped of its best players by Brooklyn in 1899, to somewhat less dramatic effect, but still enough to speed their demise.
The downsized 1900 National League allowed the Western League to fulfill its dreams of becoming a major league, filling the void in a number of cities by renaming itself the American League in 1900, and declaring itself a major league in 1901.
Pre-1886 teams
With shorter schedules before 1886, it was much more common for teams to finish with sub-.300 winning percentages, as there was less of the evening-out effect of a longer season, and some seasons had a number of teams, with nine in 1884 alone (between the three leagues that year).
In the list below (minimum 15 games played), four teams finished with worse overall winning percentages than the 1899 Spiders, but these teams played in leagues whose status as "major" is questionable: three of these occurred in the National Association (its status as a major league has long been disputed), and the other occurred in the Union Association (conventionally listed as a major league, but this status has been questioned due to the league's overall lack of playing talent and poor organizational structure).
Further to this, contemporary baseball guides did not consider the Union Association to be a major league, with the earliest record referencing the Union Association as a major league dating to 1922.