The vairable for minor civil division is clearly available for the 1% sample.
Why isn’t it also available for the larger 1940s Census or later censuses?
The availability of the MCDSTR variable is largely a function of how the data file is made available to IPUMS. In the case of the 1940 full count file, this data was made available via a partnership with Ancestry.com and we don’t have a string variable indicating the minor civil division. MCD provides information on minor civil division for many census years prior to 1940. Unfortunately for years since 1940, we don’t have data on the minor civil division.