Here is a URL that has info on the data included in each census, plus additional info. ftp://ftp.rootsweb.com/pub/roots-l/genealog/genealog.uscensus There is too much information to list here. The top of each page usually indicates the street or road for the people on the page. You need to find a map of the state, county, and townships for each census year. They changed frequently. You might also check variations in spellings of names. This causes people to not appear in a census. Actually they might be there but the census takers changed and their spelling habits weren't all the same.