Frost line depth in Baltimore County, MD
How deep the ground freezes in Baltimore County, MD
15 in. Dig to 16 in, just below the frost. Nearest NOAA station: Cylburn, 6.5 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.