Frost line depth in Darke County, OH
How deep the ground freezes in Darke County, OH
27 in. Dig to 27 in, just below the frost. Nearest NOAA station: Greenville Wtp, 2.5 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.