In just their first five seasons of existence, the Diamondbacks won three division titles (1999, 2001, & 2002) and one World Series. In 1999, Arizona won over 100 games in only its second season to win the National League West division. They lost to the New York Mets in the first round of playoffs.

In 2001, Arizona had postseason victories over the St. Louis Cardinals (3-2 in the NLDS), the Atlanta Braves (4-1 in the NLCS), to advance to the World Series where, in one of the most exciting series ever, they beat the reigning champions, the New York Yankees, 4 to 3, to become the youngest expansion franchise to win the championship.

--Wikipedia