From BR Bullpen
Initially brought on by the threat of a proposed Continental League, expansion has occurred six times in the 20th Century. In 1961, the American League added the Los Angeles Angels and Washington Senators (which replaced the previous club that became the Minnesota Twins). The New York Mets and Houston Colt .45's (later the Astros) joined the National League in 1962. For the 1969 season, the majors expanded by four teams. They were the Kansas City Royals, Montreal Expos, San Diego Padres, and Seattle Pilots (who became the Milwaukee Brewers after one season). In 1977, the Seattle Mariners and Toronto Blue Jays joined the American League. The National League added two clubs, the Colorado Rockies and the Florida Marlins, in 1993. The most recent expansion was in 1998, when the Arizona Diamondbacks and Tampa Bay Devil Rays began play.
The rosters of expansion teams are generally stocked through an expansion draft of players from existing teams. Specific procedures for the draft have varied over the years, but expansion clubs usually end up stocked with has-beens, journeymen, and young players.
Generally, expansion teams have not been competitve in their first several seasons. The Mets, who set a record for futility when they won only 40 games in their first year, finished in ninth or tenth place in the National League every season before finally winning the World Series in 1969. The Mariners were a sub-.500 club for their first 14 seasons. The more recent expansion clubs have fared a bit better. The Marlins won the World Series in their fifth season, and the Diamondbacks accomplished the feat in their fourth.
 Levels of Expansion
- Expansion of 1961 - American League expands to 10 teams
- Expansion of 1962 - National League expands to 10 teams
- Expansion of 1969 - Both leagues expand to 12 teams
- Expansion of 1977 - American League expands to 14 teams
- Expansion of 1993 - National League expands to 14 teams
- Expansion of 1998 - Major League Baseball expands to 30 teams
 Further Reading
- Frank P. Jozsa, Jr.: Major League Baseball Expansions and Relocations: A History, 1876-2008, McFarland, Jefferson, NC, 2010.
- Frank Zimniuch: Baseball's New Frontier: A History of Expansion, 1961-1998, University of Nebraska Press, Lincoln, NE, 2013. ISBN 978-0803239944