Posted On June 16, 2015
Yesterday was the first day in MLB history that all games that were played were interleague games. All 15 games yesterday were AL vs NL.
The first interleague game was on June 12, 1997 as the Texas Rangers hosted the San Francisco Giants at The Ballpark in Arlington.
For the first five seasons of interleague play, each division played against the same division from the other league (NL East vs. AL East, NL Central vs. AL Central and NL West vs. AL West). As of the 2002 season, a new format to interleague play was instituted where teams play interleague games against various divisions.
During interleague play the designated hitter rule is used in all American League ballparks, but is not used in National League stadiums. From 1997-99, umpire crews for each interleague game came from the league where the game is being played.