Subdistricts and Enumeration Districts.
As mandated by the Constitution (article I, section 2), an act of March 1, 1790 (1 Stat. 101) provided for the 1st Census and, with minor modifications, governed each census through 1850. The term "Census Office" refers to temporary staffs established to administer the decennial censuses, 1790-1900. Censuses were taken by U.S. district marshals, 1790-1870; and by enumerators under supervisors responsible through the Superintendent of the Census to the Secretary of the Interior, 1880-1900. Extant administrative records begin with those of the 4th Census (1820). Census schedules, 1790-1950, are described UNDER 29.8.
Every 10 years since 1790, the U.S. Government has taken a census to enumerate the population so as to apportion seats in the House of Representatives. Census enumerators canvass their districts house-to-house, collecting information about individuals and households on forms called population schedules.
There are hundreds of thousands of pages of Census population schedules in the custody of the National Archives. The National Archives holds original and microfilm copies of enumeration schedules from 1790 to 1870 and microfilm copies only of the 1880, 1900, 1910, and 1920 schedules. The microfilm copies of these schedules are available to researchers. Most of the 1890 census was destroyed by fire in 1921, but microfilm of surviving fragments is also open for examination. To protect the privacy of people enumerated during a census, the records are closed to research for 72 years. The release date for the 1930 census will be 2002. The schedules are part of the Records of the Bureau of the Census, Record Group 29.
From The SOURCE A Guidebook of American Genealogy (Revised Edition: Edited by Loretto Dennis Szucs and Sandra Hargreaves Luebking, Ancestry, Published 1997) page 104:
"In the days before regular mail service, government representatives conducted door-to-door canvasses of their appointed districts. Supervisors subdivided districts using existing local boundaries. The town, township, military district, ward, and precinct most often constituted one or more enumeration districts.
Boundaries of towns and other minor civil divisions, and in some cases of counties were ill defined, so enumerators were frequently uncertain whether a family resided in their own or an adjoining district. For this reason, it is not unusual to find individuals and families listed twice in the census and others missed entirely."
Subdistricts:
In most years and in most places, the census was taken on a county by county basis. In a few states and territories, such as Arizona, Louisiana, Orleans, South Carolina, and others, the county divisions have been known by other names. In other places in some years, counties have not existed or have not been used, so other means of dividing up the state or territory have been used. Common examples of these names are Beat, Division, Judicial District, District, etc.
Within the county or other major civil division many subdivisions have been used. These incluse Township, Precinct, City, Town, Village, District, Division, and Ward. From 1880 on, enumeration has been done by ED, or enumeration district.
EDs, strictly defined, were not used until the 1880 census. The early censuses used the term subdivision to refer to part of a supervisor's or marshal's division or district. Subdivisions in the early censuses comprised towns, townships, or other units comparable to MCDs (Marshall's Census Divisions or Districts).
Most early ED descriptions are general and largely served as documentation of the names of enumerators and rates of pay. They may simply state that a census taker had to enumerate an entire county or an unspecified part of a subdivision. Beginning with 1850, the ED descriptions became increasingly detailed.
Supervisor's Districts:
A supervisor's district is a large geographic area that usually covers several counties.Each state was divided into one or more large districts (SD's), then each of those into hundreds of individual districts (ED's), one per enumerator usually. So in a large state there will be several ED's, 47 for instance, in each SD. We are going to divide states into multiple pages (In our Table of Contents), and the SD is how we should do it, therefore we need to know which counties are in which SD.
Enumeration Districts:
An Enumeration District (ED) refers to the area assigned to a single census-taker to count persons and prepare schedules within one census period. It is very important to become familiar with the ED's used in the state and census year that you are transcribing (they usually differ from year to year).
