The Data Dictionary provides the necessary information to correctly use the human population and economy data, which was collated from several sources spanning a 210-year period of US history.

The data fall into five major information domains:
Population, Employment, Commercial Activities, Manufacturing Activities, Service Activities and Agriculture/Farming Activities.

The dictionary entry for each category of each domain includes the full title for the category, the short name used in the output file, the period over which the data was collected, the units and format of the data, and the original source(s) for the data. Most importantly, it contains a definition for each data collection event noting the subtle or significant changes in the meaning of terms such as commercial establishment over time.

All data are provided at a county level identified by their unique FIPS code. The data are reported by the year they were collected, which varies according to the original intent of the collection, e.g., US Population Census, US Agricultural Census, etc. However, data are retrieved by 10-year brackets. The beginning date for selection is any year ending in ‘0’ (inclusive) while the ending date for selection is any year ending in ‘0’ (exclusive, i.e., last data year would end in ‘9’). If you want 1958 commercial establishment data then make ‘1950’ your beginning of date range and ‘1960’ the end of your date range.

Population
Population, Sorted by Type (POP)
  Includes Total Population (TOT), Rural Population (FRUR), Slave Population (SPOP), Urban Population (URB)

Employment
Farm Workers (FWKR)
Commercial Employees (COMEMP)
Manufacturing Workers (MANWKR)
Service Employees (SEREMP)

Commercial Activity - Wholesale and Retail Trade
Commercial Establishments (COMEST)
Commercial Sales (COMSAL)
Commercial Wages (CWAGE)

Manufacturing Activity
Manufacturing Establishments (MANEST)
Value of Manufactured Output (MANVO)
Value Added by Manufacturing (MANVAL)
Manufacturing Wages (MWAGE)

Service Activity
Service Establishments (SEREST)
Value Added by Services (SERVAL)
Service Wages (SWAGE)

Agriculture/Farming Activity
Number of Farms (FARMS)
Farm Output (FAROUT)
Farm Product Value (FVALP)
Value of Crops (FVALC)
Farm Acreage, Sorted by Type (ACRE)
  Includes Improved Farmland (FLIMP), Unimproved Farmland (FUNIMP), Unimproved Woodland (WOODUN), Other Unimproved Farmland (FUNIO)