Decennial Census of Population and Housing
The U.S. census counts every resident in the United States. It is mandated by Article I, Section 2 of the Constitution and takes place every 10 years.
2020 Census Decade: About the 2020 Census
Here is an overview of the 2020 Decennial Census.
The data on race and ethnicity were derived from answers to the question on race and ethnicity that was asked of individuals in the United States.