Many genealogists rank censuses among the most-useful US records for good reason. Taken every 10 years, the federal census provides an unparalleled snapshot of families at regular intervals.
In addition to census returns, though, researchers can access another helpful resource from the census-taking process: enumeration district maps (ED maps). These illustrated for census officials where they would be going door to door—and, like the censuses themselves, provide information about the area and the people who lived there.
In this article, we’ll cover how ED maps were created, what you can use them for, and how to access and read them today.
What are Enumeration Districts?
Since 1880, the U.S. Census Bureau has divided states into enumeration districts (EDs) to organize enumerators’ efforts. Each ED was sized such that one census-taker (enumerator) could count the district’s population within the census period of two to four weeks.
Each ED was assigned a number—for example, 2-8. The first number usually referred to the county, and the second number to an area within that county. Census-takers did not use the same EDs from decade to decade; EDs changed in response to demographic shifts and the Census Bureau’s needs.
Note also that EDs were unique to areas within each state. California and Ohio each had an ED 1-14 in the 1950 census, for example: California’s 1-14 was part of the city of Hayward near San Francisco, and Ohio’s 1-14 was in Lima (nearly 2,300 miles away).
The Census Bureau created ED maps that display the boundaries and numbers of each ED in an area. On the ED map below (from Allen County, Ohio, in 1940), ED numbers are larger and lighter than the other type on the page. ED boundaries—which are usually along roads, railroad tracks, or borders of political jurisdictions—are in black.
What Enumeration District Maps Can Tell You
ED maps are valuable companions in census research. In addition to illustrating the enumeration process, the maps depict your ancestor’s neighborhood at the time he lived there. As with contemporary street maps, you can see a sketch of local landmarks, churches, schools and businesses.
In addition, because districts were drawn to be enumerated by one person, the size of an ED reflects how many people lived within it. Large EDs tended to have a low population density, while small EDs had a high population density. In the map above, the shaded area—the city of Lima, Ohio—is comprised of ED numbers 2-21 through 2-56. By contrast, the (more-rural) area around the city has fewer—but larger—EDs.
Finally, ED maps are critical for browsing census images, such as in situations where keyword-searches aren’t producing the results you hoped for. On sites such as FamilySearch and Ancestry.com, microfilmed images are organized first by state, county, locale, then ED. Knowing your ancestor’s ED will save you from having to scroll images from multiple places, especially in urban areas.
How to Find an Enumeration District Number
To browse census records and/or put your ancestor’s home in context, you’ll need to know his address (or, at minimum, the city, town or county). Street and house numbers are listed in census records next to each family, though you may need to page backward in an image collection to see them.
Once you have an address, the easiest way to find an ED number is by using Stephen P. Morse’s Unified Census ED Finder. Simply select a census year (1870–1950) from the drop-down, then indicate the state. The tool requires you to select at least a city or town name, but you can also select a county. Enter house number and street name in the appropriate boxes, if you know them.
Your results will include all the ED numbers that correspond to your location. The more details you can provide, the fewer (and more-accurate) ED numbers you’ll see. Click an ED number to access the relevant census images from FamilySearch, Ancestry.com and (for some) the National Archives.
Where to Find Enumeration District Maps Online
Most surviving ED maps held by the National Archives. NARA’s collection has only partially been digitized, however; you can view some ED maps by county on NARA’s website. The 1950 census has its own portal, where you can filter by state and ED. Entries include a description of the ED plus links to both ED maps and census population schedules.
The viewing experience is easier through NARA’s partner websites. On FamilySearch, you can browse a collection of these maps from the censuses taken between 1910 and 1940, organized by state and county. Ancestry.com has ED maps for just the 1940 census.
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A version of this article appeared in the December 2015 issue of Family Tree Magazine. Last updated: July 2025.
