Frost line depth in Lincoln County, MO
How deep the ground freezes in Lincoln County, MO
22 in. Dig to 23 in, just below the frost. Nearest NOAA station: Elsberry 1 S, 11.6 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.