http://www.stevemorse.org/ This has all kinds of interesting stuff. Most of it is free, except some that hooks up to Ancestry. But, it has a section that explains what all those codes are on the 1930 census under A, B, C and D. Scroll down to 1930 Census Codes under US Census and Soundex. They have to do with Occupation, Language, state & country of birth, Indian tribes. Maybe Lee has sent this before. If so, I failed to check it out. Cynthia