What is the explanation of all of the various numbers that appear in those columns labeled Leave Blank?
"Labeled A through H between the numbered columns, these sections were filled after the census was taken to clarify entries in other columns. For example, column C included three codes for eligible respondents: occupation, industry and code."
Yes, but I just finished reviewing a "family" of 30 soldiers on a military base. The State names were all blank and the OCR column B values were mostly incorrect. After correcting Col B values, I found the state numbers on SteveMorse.org and was able to correctly fill in the state names of the birthplaces. The race, sex and marital status were all numbers as well. For marital status, 5=Never Married and 3=Divorced.
Attached is the text file I was able to put together from SteveMorse.org and elsewhere. It might be of help to someone else.