The Tigers pressure defense forced 33 North Andrew turnovers. Offensively, Walnut Grove (28-4) shot 52-percent from the field.
Katie Cole led the Cardinals (29-3) with 17 points and nine rebounds. Kensey Edwards added 16 points.
Walnut Grove jumped ahead 25-11 at the end of the first quarter, and was in control 45-25 at halftime.
Heather Harman, who will be playing basketball at Division II Drury University next season, had a game-high 30 points and seven assists.
The second place finish is the best in program history for North Andrew. The Cardinals graduate Danielle Chambers, Autumn Hughes, Brinsley Oliver and Angel Singleton off this year's squad.