Interleague play
In 1999, Major League Baseball expanded Interleague play, allowing the Mets and Yankees to host a series at their home stadiums. At Shea, the Mets won their first series against the Yankees, 2 games to 1, though the regular season series was tied by virtue of a Yankees series win (2–1) at Yankee Stadium earlier that year. That year marked the first time both teams reached the playoffs in the same season, though the Mets needed an extra game for their first playoff appearance since losing the 1988 National League Championship Series.