Downloadable files with loan limits for each “Effective Period”, with complete listings of all counties, their loan limits, and the median prices used to determine those limits are available at https://www.hud.gov/pub/chums/file_layouts.html
The website has loan limit files for FHA forward loans, FHA HECM, and Fannie Mae and Freddie Mac purchases, with individual records at the county level.
For counties within metropolitan areas as designated by the Office of Management and Budget, loan limits are determined by the high-price county within the metropolitan area.
To determine if a county is within one of the metropolitan (or micropolitan) areas, you should check the FHA mortgage limits at https://entp.hud.gov/idapp/html/hicostlook.cfm
For additional information see the Maximum Mortgage Limits web page at https://www.hud.gov/program_offices/housing/sfh/lender/origination/mortgage_limits
Handbook 4000.1 II.A.2.a.ii. is available at https://www.hud.gov/program_offices/administration/hudclips/handbooks/hsgh