Frost line depth in Mineral County, CO
How deep the ground freezes in Mineral County, CO
57 in. Dig to 57 in, just below the frost. Nearest NOAA station: Hermit 8 Se, 14.7 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.