The National League would stay operational with eight teams until 1962, but not all of the initial clubs were still operating at the time. The league's first expansion occurred in 1962, with the arrival of the New York Mets and the Houston Colt.45s, eventually known as the Astros. Another team, the San Diego Padres, joined the league in 1969.
An eighth team began play in Montreal in 1961. However, after two seasons, the club withdrew from the league and replaced it with the Houston Oilers/Tennesse Titans NFL franchise. The Titans failed to reach an agreement on a stadium lease with the city of Montreal, and instead played their home games for one season (1970) at Tulane University's Tuller Field before leaving Canada to become the Oakland Raiders (now the Los Angeles Rams).
The current configuration of the NL came about as a result of a major realignment of the MLB following the 1957 season. That year, the New York Yankees, who had dominated baseball throughout the 1940s and 1950s, fell short of winning their third straight World Series title when they lost to the Brooklyn Dodgers. The Yankees' loss was seen by many as a miscarriage of justice--after all, they had beaten the Dodgers four out of five times during the series--and prompted several changes in MLB policy.
With the advent of the Houston Colt '45s (later Astros) and the New York Metropolitans in 1962, the National League grew to ten clubs (Mets). In 1961, the American League schedule was expanded to include each club playing each other 18 times. The remaining game between the two league champions was called the World Series.
The number of teams in both leagues increased from nine to ten shortly after the start of the 1960 season when the Milwaukee Braves moved to Atlanta and the New York Yankees left for Bronx County Stadium in New York City. The American League added a team when the Baltimore Orioles came into existence in 1953. The National League followed suit with a new franchise named after its latest world championship team - the Cincinnati Reds. The Reds played their first game on April 17,1953, at Crosley Field against the Chicago Cubs. The last game of the old Boston Braves' season took place on September 30,1957, at Braves Field where they were defeated by the St. Louis Cardinals 4-3 in 11 innings. The number of games per season decreased from 154 to 150 due to the addition of an extra game in 1997 and 1998 to determine the World Series champion.
There have been proposals to add more teams to both leagues but none have come to fruition. In 1992, there were discussions about moving one of the existing teams - the Cleveland Indians - to Toronto but these plans fell through.
From 1900 through 1961, the National League was comprised of eight teams. The National League contracted once more in 1900, this time to eight clubs. The roster contained the two original NL clubs, Boston and Chicago, as well as six American Association teams: Brooklyn, Cincinnati, New York, Philadelphia, Pittsburgh, and St. Louis. After the 1899 season, the Buffalo Bisons moved to New York and were renamed the New York Giants.
The league expanded again in 1960, when the Milwaukee Braves joined the National League. The AL had only five teams then; however, the Braves were not allowed to compete until 1962 because of a major league reserve clause that prevented players from moving from one team to another within the same league. The reserve clause was ruled illegal by an arbitrator in 1974, but it took until 1978 before the last remaining reserve clause case was settled out of court.
In 1991, the Montreal Expos joined the NL, but they were relocated to Washington D.C. and became the Washington Nationals in 2005. The Tampa Bay Rays joined the AL in 2002, so there are now 12 teams in each league.
There have been many rumors that have surfaced over the years about other teams joining either the AL or NL. In 1957, there were even talks about merging the two leagues into one 16-team league. But none of these ideas ever came to fruition.
Major League Baseball was poised to grow again by the late 1960s. Both leagues decided in 1967 to add two additional clubs, for a total of 12 teams in each league. The Athletics' relocation to Oakland hastened the expansion process. The new teams were to be named after Native Americans; they would be called Indians, Braves, and Phillies in the American League and Reds, Giants, and Pirates in the National League.
The original eight teams were Boston (American League), Chicago (American League), Cincinnati (National), Detroit (American League), Philadelphia (American League), Pittsburgh (National), St. Louis (American League), and Washington (National). The addition of these four teams expanded the league into a split season format for the first time since 1899. The American League champion would then meet the National League champion in the World Series.
In 1968, the Athletics moved to Oakland. They were replaced that year by the San Francisco Giants, who had been founded in 1883 but had never played in San Francisco because of financial problems. The Giants eventually settled on New York as their home city, although they have also played in San Francisco and Baltimore. The Atlanta Braves relocated from New York following the 1957 season when their parent club, the Braves franchise name, moved to Milwaukee.