May 27, 1968: National League announces the addition of Montreal and San Diego, to begin play in 1969 as the Expos and the Padres, respectively. The Kansas City Royals and short-lived Seattle Pilots would join the American League at the same time. That spurred the formation of East and West Divisions in each league for the first time (and, consequently the AL and NL Championship Series). The Expos were Major League Baseball’s first franchise in Canada and played 36 seasons there before moving to Washington in 2005 and becoming the Nationals.
The Pilots lasted just one year in Seattle before becoming the Milwaukee Brewers in 1970. They played in tiny Sicks Stadium with hopes that a new ballpark would be built. King County voters had approved the domed stadium that would become the Kingdome, but the team was bleeding money, and construction was too far off for the team to last in Sicks, a 25,000-seat crackerbox. On April 1, 1970, six days before Opening Day, the Pilots were declared bankrupt, clearing the way for them to move to Milwaukee and the waiting arms of Bud Selig, who had been working to get them all winter.
Seattle finally got a team for good in 1977, when the Mariners were born in the one-year-old Kingdome (along with the Toronto Blue Jays). The National League finally matched the AL’s 14 teams in 1993 when it added the Colorado Rockies and the Florida Marlins. The most recent expansion was in 1998, when the Tampa Bay Devil Rays debuted in the AL and the Arizona Diamondbacks were added in the NL.
Baseball’s first expansion came in 1961, when the American League added the Los Angeles Angels and the second iteration of the Washington Senators. The original Senators moved to Minnesota that year and became the Twins. The National League followed in 1962 with the New York Mets and the Houston Colt 45s (now the Astros). There were several franchise shifts in each league before that, but otherwise the NL and AL had remained static with eight teams apiece since the beginning of the 20th century.
(Tom Scott hosts the Scott Slant segment during the football season on KTVB’s Sunday Sports Extra. He also anchors four sports segments each weekday on 95.3 FM KTIK and one on News/Talk KBOI. His Scott Slant column runs every Wednesday.)