1962: Houston Colt .45s and New York Mets enfranchised 1965: Houston Colt .45s renamed Astros 1966: Milwaukee Braves move to Atlanta 1969: Montreal Expos and San Diego Padres enfranchised 1993: Colorado Rockies and Florida Marlins enfranchised 1998: Arizona Diamondbacks enfranchised 1998: Milwaukee Brewers transfer from the American League. (Before the 1998 season, the American League and the National League each added a fifteenth team. Because of the odd number of teams, only seven games could possibly be scheduled in each league on any given day.