A census is "an official accounting of population." In the United States, Article I, Section two of the Constitution mandates that a census is taken every 10 years. The primary purpose of the census is to determine the apportionment of taxes and representation in Congress. The first census was conducted in 1790.
Because of the complex social changes that have taken place within the United States over the course of time, researchers should bring an awareness of history into the evaluation of census data. For the Sundown Towns assignment, this type of critical evaluation is absolutely necessary.
The National Archives and Records Administration provides the following general limitations of the United States Census. These limitations should be kept in mind when evaluating places to classify them as "Sundown Times"
Source: African Americans in the Federal Census, 1790-1830: Using Federal Census Records to Find Information on African American Ancestors