Frost line depth in Nelson County, ND
How deep the ground freezes in Nelson County, ND
73 in. Dig to 73 in, just below the frost. Nearest NOAA station: Petersburg 2 N, 12.1 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.