Frost line depth in Hubbard County, MN
How deep the ground freezes in Hubbard County, MN
66 in. Dig to 66 in, just below the frost. Nearest NOAA station: Park Rapids Muni Ap, 15.3 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.