Players Protective Association
The Players Protective Association was an early form of a Players' Association, active around the beginning of the 20th Century. It was founded on June 9, 1900, with Chief Zimmer as its founding President and had its greatest influence when the minor league American League decided to become a major league in 1901, by moving into some of the larger National League cities and entering teams in some of the cities abandoned when the NL contracted after the 1899 season.
The main areas of demand for the Association were the reserve clause, which bound players to their present team theoretically in perpetuity, and salary levels kept artificially low by collusion among team owners and the lack of open competition. The creation of the American League meant that dissatisfied National League players could, for a while, jump their contracts and seek better terms with teams in the new circuit. A number of prominent stars did just that, including future Hall of Famers Cy Young, Jimmie Collins, Jack Chesbro, Sam Thompson, Elmer Flick and Napoleon Lajoie. These sometimes led to lawsuits - most famously in Lajoie's case - until the two leagues made peace in 1903 and agreed to respect each other's contracts. The Association's power waned significantly after that, and attempts to unionize players would sputter with little success until the late 1950s when the issue of inadequate player pensions galvanized players into collective action.