Are precinct level data available for counties in each of the 1900-1940 full count Census datasets? The 1930 Population Bulletin includes the data of population by county precincts. I would like to get the full count by age and sex by precinct for those years.
The county election precinct that a respondent was enumerated in is identified in the IPUMS USA historical representative samples in the variable MCD (Minor Civil Division). Specifically, MCD is reported in samples from 1850-1930 that range in density from 1% to 10% of the total population (1% - 5% in 1900-1930). These samples were systematically drawn from the full data and should give you a reasonable estimate of the true values from the full count.
The IPUMS USA public use full count microdata does not report the MCD, however it is available in the restricted use full count data. The data requires an institutional license and includes a license fee; please email us at ipums@umn.edu if you would like to apply for a license and I will share the application materials.
If you prefer to continue using the public full count data, then you may be able to leverage the reported enumeration district (ENUMDIST) of residence that is available for all records from 1880-1950. These districts were created for each decennial census often by drawing from existing election precinct boundaries. In some cases, a district maps one-to-one onto a precinct. Other times a district may include multiple precincts in full or parts of several different precincts. Depending on how neatly these map in your counties of interest, you might try reconstructing precinct boundaries from these enumeration district identifiers. In my experience, the Unified Census ED Finder tool on Stevemorse.com can be very helpful for this type of analysis. This scanned document describing 1930 & 1940 enumeration district boundaries should be particularly helpful since it notes the correspondence between the districts and precincts. The Unified Census ED Finder tool might also help you find the descriptions for earlier years as well.