Mandan and Bismarck each won a game of a doubleheader at the Bismarck Athletic Complex on May 5.
After losing the first game 5-4, Bismarck responded with a win in Game 2.
With the game tied at 1 in the bottom of the third, the Demons pushed across two runs take a 3-1 advantage.
Bismarck earned a split with a 6-4 win.
Bismarck, now fourth in the West at 12-8, plays Century on May 9.
Mandan, at 12-10, is home against Minot on May 9.