My main interest in this post is how to access the manuscript census. There are three methods for accessing census records, geographically, alphabetically, and Soundex.
First of all, the records are organized geographically. By looking at indices or the online versions, the arrangement may not be evident, but if you look at the header or the masthead of each census sheet, you find some indication of the location the sheet describes. State, County, Township or Ward are all identified along with the enumeration district and supervisor district. Along the left hand margin you often find the name of the street. You'll find street and family numbers also. If you know where an individual lived, you can access the census geographically using first city directories to narrow down street locations, then enumeration district descriptions to know which enumeration district to look for. Stephen Morse's site provides links to enumeration district descriptions http://www.stevenmorse.org/census/index.html and has an enumeration district conversion chart http://www.stevenmorse.org/census/ed2040.php. If you are using microfilm, identifying information on the rolls list enumeration districts. I have simple instructions on how to do this type of search manually (using paper records) on my website http://www.mbkcons.com/wkshp/geneaology/1930censuswith1920examples.htm . Heritage Quest and Ancestry provide Browsing options by geographical location. (If you know the enumeration district, you can search for the digitized census on Internet Archive http://archive.org/details/us_census. Stephen Morse's site also has links to the rolls of digitized microfilm by geographical description http://www.stevenmorse.org/census/censusbrowser.html Once you identify the geographical location and the roll of microfilm or the digital file, you'll have to look through the census sheets. Enumeration districts contain about 5000 names or for rural areas, one township.
The easiest access method is alphabetical which requires the use of indices both print and online. Not all indices are created equal. Some indices list the head of the household only and other individuals if they fit various criteria, age, different names or different races. If you are using a print index, the front matter or introduction should tell you how that census decade is indexed, the criteria for listing names, and all abbreviations. For example, the 1880 print index for Ohio is an "every name" index, but the 1870 index lists heads of household only, except for those with different surnames, men over 50, and women over 70, changes in race or color, individuals living in an institution such as an orphanage, hospital, or poor house. (Ohio 1870 Census Index. Vol. 1 A-Comric. Edited by Raeone Christensen Steuart. Bountiful, Utah: Heritage Quest, 1999, p. xi)
Alphabetical access to online censuses are a given. FamilySearch, Ancestry, and Heritage Quest all provide easy access to census records by indexing surname and given name. They do index other fields but you cannot search on those fields. For example, you cannot search for the names of all people born in Germany in a certain decade. For that information, you need to look at the statistical reports of the census, which do not provide individual names. However, none of the databases tell you what criteria are used for indexing the census and indeed if they only index head of household. There have been some recent articles indicating that Ancestry particularly is going back and re-indexing earlier census decades to include all names. It is important to go beyond the abstract or index screen, and read the entire entry on the manuscript census.
The third method for accessing the census is Soundex (or Miracode in 1910). This is an alphanumeric system for coding names, particularly European names based upon the way they sound and then organizing the codes by state, numerically and then by first name.Claire Prechtel-Kluskens writes about the Soundex projects in “The WPA Census Soundexing Projects” Prologue Vol. 34, No. 1 (Spring 2002) http://www.archives.gov/publications/prologue/2002/spring/soundex-projects.html Once you find the Soundex record or abstract, you need to go to the actual census record to examine all the information collected the census takers.
You could spend a lifetime studying the census and all the clues hidden within. Take time to think about what individuals said about themselves and their households. Explore their neighbors and communities by scrolling (either in microfilm or online) and examining the entire enumeration district. Most importantly, if you don't find the person(s) you are looking for through the alphabetical index, whether in print or online, look at the actual census records. There are many spelling errors and typos in the indices and databases, your ancestors pronounced and spelled their names differently than you might today. Question the indices, the Soundex, and the actual census entries. You never know what's hidden within. Good luck.
My next entries will talk about searching for and analyzing vital records.