Frost line depth in St. Francois County, MO
How deep the ground freezes in St. Francois County, MO
19 in. Dig to 19 in, just below the frost. Nearest NOAA station: Farmington, 3.7 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.