Frost line depth in Marshall County, MN
How deep the ground freezes in Marshall County, MN
67 in. Dig to 67 in, just below the frost. Nearest NOAA station: Agassiz Refuge, 17.8 mi.
Your building department sets the legal frost line depth (IRC Table R301.2(1)); footings must go below it (R403.1.4.1). Call them before you dig.