Page "Arizona Diamondbacks" Paragraph 9

Arizona had originally been intended to join Tampa Bay in the American League.

However, five American League teams had threatened to block the league assignments because of concerns that they would have additional games out of their time zone, causing early starts that would decrease revenue and TV ratings.

Thus, on January 16, 1997, the Diamondbacks were officially voted into the National League while their expansion counterparts in Tampa Bay were voted into the American League.