Note that regional categories have the structure:
States
Counties
MSAs
BEA Economic Areas
Basic Trading Areas
Census Regions
Census Divisions
BEA Regions
Federal Reserve Districts
States in District
Counties in District
MSAs in District
Specific geographies have been omitted for brevity. As an example, 'St. Louis' county in the state of Missouri has the category path:
States >Missouri >Counties >St. Louis County, MO