1820 United States census

1820 United States census
← 1810 August 7, 1820 (1820-08-07) 1830 →
Seal of the United States Marshals Service, which administered the census
General information
Country	United States
Authority	Office of the United States Marshal
Results
Total population	9,638,454 ( 33.1%)
Most populous ​state	New York 1,532,881
Least populous ​state	Illinois 55,211

The 1820 United States census was the fourth census conducted in the United States. It was conducted on August 7, 1820. The 1820 census included six new states: Louisiana, Indiana, Mississippi, Illinois, Alabama and Maine. There has been a district wide loss of 1820 census records for Arkansas Territory, Missouri Territory,^[1] and New Jersey.

The total population was determined to be 9,638,453, of which 1,538,022 were slaves. The center of population was about 120 miles (193 km) west-northwest of Washington in Hardy County, Virginia (now in West Virginia).

This was the first census in which any states recorded a population of over one million—New York, Virginia, and Pennsylvania—as well as the first in which a city recorded a population of over 100,000—New York. It was also the first census in which Baltimore was ranked as the country's second-most populous city. Thirdly, in this census and the 14 subsequent ones, New York was the most populous state until being superseded by California in the 1970 census.