After the 1957 season, the Brooklyn Dodgers and New York Giants relocated from New York to California to become the Los Angeles Dodgers and San Francisco Giants, respectively, leaving the largest city in the United States with no National League franchise and only one major league team (the American League (AL)’s New York Yankees). With the threat of a New York team in a third league, the National League expanded, adding the New York Mets after requests from William Shea. The new team took as its primary colors the blue of the Dodgers and the orange of the Giants (which are also two of the three colors on the New York City flag), and took their name from a 19th-century club, the New York Metropolitans.

For the first two years of its existence, the team played its home games at the historic Polo Grounds in Upper Manhattan. In 1964, they moved into newly constructed Shea Stadium in Flushing, Queens, where the Mets played through the 2008 season. William A. Shea Municipal Stadium, usually shortened to Shea Stadium or just Shea, was a stadium in the New York City borough of Queens, in Flushing Meadows–Corona Park. It was the home baseball park of Major League Baseball’s New York Mets from 1964 to 2008. Originally built as a multi-purpose stadium, Shea was also the home of the New York Jets football team from 1964 to 1983. It was named in honor of William A. Shea, the man who brought National League baseball back to New York. It was demolished in 2009 to furnish additional parking for the adjacent Citi Field, the current home of the Mets.

The 1969 World Series was played between the New York Mets and the Baltimore Orioles, with the Mets prevailing in five games to accomplish one of the greatest upsets in Series history, as that particular Orioles squad was considered to be one of the finest ever and still is by some baseball pundits. The World Series win earned the team the sobriquet “Miracle Mets,” as they had risen from the depths of mediocrity the 1969 team had the first winning record in Mets history.

The 1986 World Series pitted the National League champion New York Mets against the American League champion Boston Red Sox. The Mets won the Series in the seventh game, after overcoming a nearly hopeless deficit in Game 6, culminating in a late-game error by Boston’s first baseman Bill Buckner. Game 6 was also cited in the legend of the “Curse of the Bambino” to explain the error.

The 2009 season was the Mets’ first season at Citi Field, a retropark following current architectural trends in stadium design. It follows the brick and steel-truss trend begun by the Orioles at Oriole Park at Camden Yards in 1992. The exterior facade resembles Ebbets Field, former home of the Brooklyn Dodgers. The Mets’ first exhibition game at Citi Field was played on April 3, 2009 against the Boston Red Sox. The first regular season home game was on April 13, 2009 against the San Diego Padres, who spoiled the opener with a 6–5 win against the Mets. In that game, Jody Gerut of the Padres became the first player to open a new ballpark with a leadoff home run. On April 17, Gary Sheffield, who just days earlier was signed by the Mets as a free agent, hit his 500th home run against the Milwaukee Brewers. Sheffield became the first pinch hitter to reach this milestone, as well as the first to do it in a Mets uniform.