The 2020 U.S. Census will ask respondents if they are American citizens.
The Trump administration announced late Monday it plans to reinstate a question about citizenship at the request of the Justice Department.
The administration says the citizenship data is needed to "help enforce the Voting Rights Act," which protects minority voting rights.
Among other things, census data is used to determine how federal funds are spent, political representation in Congress, and the size of the country's population.
But some say that data could get skewed if immigrants don't fill out the census because they're worried about a citizenship question.
A group of state attorneys general and the governor of Colorado sent a letter to Commerce Secretary Wilbur Ross in February, asking him not to reinstate the question for that very reason.
In a statement, the Commerce Department said Ross decided getting "complete and accurate information ... outweighed the limited potential adverse impacts."
It noted that a citizenship question was asked on almost every decennial census from 1820 to 1950.