"There were no specific instructions issued to census takers until 1820." -- U.S. Department of Commerce. Bureau of the Census. 200 Years of U.S. Census Taking: Population and Housing Questions, 1790-1990. 1989.
United States Enumeration District Maps for the Twelfth through the Sixteenth US Censuses, 1900-1940. FamilySearch. Citing NARA microfilm publication A3378. About the microfilm.
Finding ED Definitions for [1880/1900/1910/1920/1930/1940/1950] in One Step. Stephen P. Morse and Joel D. Weintraub.
Provides text descriptions of the boundaries of Enumeration Districts.
Map guide to the U.S. federal censuses, 1790-1920. Print.
Main Libr folio G1201.F7 T5 1987
All U.S. county maps 1790-1920. Historical county boundary lines superimposed on modern ones.