Rain forced the game to start 43 minutes late and also delayed the game before restarting in the fourth inning at 9:05 pm.
Joliet scored three in the fifth and three more in the seventh to take a 6-4 lead into the eighth inning.
Reliever of the year Ryan Quigley pitched the ninth and recorded his fifth save of the postseason.
Brad Netzel, who graduated from the University of St. Francis in Joliet, was named the championship Most Valuable Player.
