Frost line depth in Ralls County, MO
How deep the ground freezes in Ralls County, MO
17 in. Dig to 17 in, just below the frost. Nearest NOAA station: Monroe City, 12 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.