In working with manuscript census materials, modern data derived from them, and published documents from the Census Bureau, I found myself coming back to particular resources time and again. In a hope this might be of use to someone else, I've put together this list of those I use most frequently. If you have suggestions or corrections, please contact me or leave a note in the comments, below.

Manuscript materials

  • Main page for manuscript population schedules, 1790--1930, digitized from NARA microfilm, hosted on the Internet Archive: https://archive.org/details/us_census

  • The 1940 manuscript census, with full access provided at no charge by NARA.

  • The Unified Enumeration District Finder -- choose the desired year in the dropdown box in the title. Helps you find Enumeration Districts from addresses, for 1880-1940 censuses. In other words, you use this to help you find a key piece of information necessary to allow you to look up a particular place in the census. A quirky but amazing site.

  • Modern re-creations of census forms, helpful for deciphering questions (i.e. these are readable, but double-check each against an original) or for taking notes on a limited number of people: http://www.cyndislist.com/us/census/forms/

Data sources

U.S. Census publications

  • Census Bureau: Published books from the census, in annoying linked PDF format: http://www.census.gov/prod/www/decennial.html (or via FTP here). The Dubester catalog is helpful in figuring out what's what, and what is missing. There is data available in tabular form in these publications that hasn't made its way to the databases, so it can still be helpful to access them. These particular scans are not high quality, unfortunately, but far better than no access at all.

  • Census Bureau Library, on archive.org. Contains mostly mid-late 20th century reports. Difficult to search, as may be imagined. https://archive.org/details/CensusBureauLibrary

  • Census Bureau FTP site, includes many historic publications (note, mirrored on IA in a huge tarball): ftp://ftp.census.gov

  • Henry J. Dubester, Catalog of United States Census Publications, 1790-1945 (Washington: GPO, 1950). The standard, though the Census Bureau has stopped listing the Dubester numbers for early publications on their site, so it's not quite as important to use it to navigate. Still helpful to make sure you have seen what there is to see, and to help decipher similarly-named documents. Available as one half of this huge PDF, or at HathiTrust (Note: The first link above has a second piece that picks up where Dubester left off and continues to 1972.) Kevin Cook published a revised version in 1996 that provides SuDoc numbers for the publications listed by Dubester, making them much easier to find in a modern Government Publications depository library.

  • Henry J. Dubester, State Censuses: An Annotated Bibliography of Census of Population Taken After the Year 1790 by States and Territories of the United States (Washington, DC: Government Printing Office, 1948), 73 pages. Google Books

  • Yearly Catalogs of Census publications (more recent era): https://www.census.gov/prod/www/catalogs.html

  • Jason G. Gauthier, Measuring America: The Decennial Censuses from 1790 to 2000 ([Washington]: U.S. Census Bureau, 2002), http://www.census.gov/prod/2002pubs/pol02-ma.pdf This is a very detailed chronology of census information that can be quite helpful in figuring out exactly what was asked when, and what survived. Includes images of the population schedules.

Commercial services

I try to avoid these, but especially if you are trying to trace the history of a particular individual, they are powerful and can save you some legwork. Note that if you happen to be in the vicinity of a National Archives facility, you can use them (and others) for free on-site, as part of a deal struck when NARA began permitting the companies to digitize NARA records in huge batches.