Frost line depth in Woodford County, IL
How deep the ground freezes in Woodford County, IL
29 in. Dig to 29 in, just below the frost. Nearest NOAA station: Congerville 2nw, 11.8 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.