Now that you have identified the names of the people you want to find and have their addresses you need to discover in what Enumeration District (ED) they may be listed on the census. Knowing the ED narrows your search down to a few dozen pages instead of hundreds.
The best way to locate the ED is to check Steve Morse's Unified 1940 Census ED Finder. There are several possible ways to address the problem on this web page. The first is to use the Enumeration District from the 1930 census to locate possible EDs in the 1940. Under If you know the 1930 ED for this location, enter it here, select the state, and enter the county and 1930 ED. Since the 1940 census is not available, select 1940 ED Description, and click More Details. A description of the probably 1940 ED will appear, if available. Unfortunately, this method does not always produce results.
The much better method is the Enter as much of the 1940 location as you know concerning the location: State, county, city or town, then address. Then click Get ED Numbers. If more than one ED is possible, you will be prompted to enter cross-streets to narrow the possibilities. Using a current map (perhaps using Google Maps online) can aid in determining cross streets.
If the address was outside city limits, or if you would like to study the area, the ED maps are the next step. At the Unified Census Finder main page, select ED Maps. Select the state and county. A new page will open listing links for the maps available for the area. Each map is slightly different, with the first several as overview maps and subsequent maps showing more detail. Once the map appears, it will either be almost too large to find anything, or so small that the street names cannot be read. I strongly suggest saving the images to a USB drive as a JPeg, then opening that saved image to better browse the image. Remember that these maps, both online and as saved images, are large and take a while to open and stabilize. Be patient. Using current maps alongside the ED maps will enable you to
The 1940 census will be available on April 2, at 9 AM at the National Archives, where there is a downloadable 1940 Census template, and very shortly thereafter at Archives.com. Both of these sites will offer free access. The images will also be available at FamilySearch and Ancestry shortly after that. Since the census will not be indexed at that time, locating possible EDs are vital to narrow your search. If you do not have possible locations, do not despair! As soon as the census is released on April 2nd, the 1940 Census Community Project will commence. This joint initiative between Archives.com, Family Search, findmypast.com, and other leading genealogy organizations to create a free index. If you do not know where to find your ancestors, or even if you do but still want to help, you might volunteer to assist in this important project.