Frost line depth in Platte County, WY
How deep the ground freezes in Platte County, WY
28 in. Dig to 29 in, just below the frost. Nearest NOAA station: Wheatland 4 N, 1.5 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.