Along with the Florida Complex League (FCL), it forms the lowest rung on the North American minor-league ladder.

The league began play in 1988 as the Arizona League (AZL) on an experimental basis with four teams playing a 60-game schedule—the teams were affiliated with the Milwaukee Brewers, Oakland Athletics, San Diego Padres, and a cooperative between the Boston Red Sox and Seattle Mariners.

A crowd of 6,124 attended the Diamondbacks' first game on June 25, 1996, a 15–7 loss to the Phoenix Athletics.

A number of local dignitaries were at the game, including Buck Showalter and Jerry Colangelo.

The team, composed of the Rockies' first-ever draft picks, received a different level of notoriety than the Diamondbacks for their first rookie league game: as the players wore either Rockies jerseys or Cubs jerseys, the team did not have their uniform pants ready at the start of the season, and had to borrow pants from the Cubs.

[6] Between 1998 and 2000 an unaffiliated team composed of young players from the Mexican League played out of the Tucson Electric Park spring training complex, in part to add a fourth team to a southern division.

Three Tucson-based teams (the Mexican All-Stars, the Diamondbacks, and the Rockies) would leave the league after the 2000 season, largely due to travel concerns, followed by the White Sox two years later.

[12] Teams in the league are not referred to by their home city, but simply by their parent club's name.