1840 United States census

The 1840 United States census was the sixth census of the United States. Conducted by U.S. marshals on June 1, 1840, it determined the resident population of the United States to be 17,069,453 – an increase of 32.7 percent over the 12,866,020 persons enumerated during the 1830 census. This census showed that the total population included 2,487,355 slaves.

Important milestones of this census included several firsts: a state recorded a population of over two million (New York), a city recorded a population of over 300,000 (New York), and multiple cities recorded populations of over 100,000 (New York, Baltimore, and New Orleans).

This was also the last census conducted by U.S. marshals. Starting in 1850, a temporary office would be set up for each census under the Department of the Interior. This change happened because some members of the Whig Party disagreed with a claim in the 1840 census about Black Americans in the Northern United States.

Controversy over statistics for mental illness among Northern blacks

The 1840 census was the first to try counting Americans who were considered "insane" or "idiotic." The results showed many Black people in non-slaveholding states were reported as mentally ill, unlike in slaveholding states.

Pro-slavery groups used these numbers to claim slavery was good, while anti-slavery groups argued the data was wrong. They asked Congress to fix the mistakes, but the census results were not changed.

Census questions

The 1840 United States census asked about several details of each family and its members. It collected the name and address of the head of the family, and the number of free white males and females in different age groups.

The census also counted the number of slaves and free colored persons, as well as people who were deaf, blind, or unable to read and write. It recorded the jobs people had and how many schools and students there were in the area.

Data availability

No detailed records from the 1840 United States census are available, but general population numbers for smaller areas can be found online through the National Historical Geographic Information System. The Census Bureau also has a collection of data from this census, organized by states, counties, and major towns, available on the web site of the Census Bureau.

State rankings

The 1840 United States census counted the people living in the country on June 1, 1840. It found that 17,069,453 people were living in the United States, which was an increase of 32.7 percent from the previous census in 1830. Among these people, 2,487,355 were slaves. This information helped leaders understand how the population was growing and where people lived.

City rankings

The 1840 United States census recorded the country’s population and ranked its largest cities. This information helped leaders understand where people lived and plan for future growth. The data showed which cities were growing fastest and which were still small, giving a clear picture of the nation at that time.