Updated Tuesday at 6:43 p.m. ET

To help figure out the U.S. citizenship status of every adult living in the country, the Trump administration has been accumulating driver's license information from states including South Dakota, NPR has learned.

South Dakota Public Safety Secretary Craig Price — who was appointed to President Trump's commission on law enforcement earlier this year — signed an agreement in April to share information from driver's licenses and state ID cards with the U.S. Census Bureau, according to a copy of the memorandum of understanding the state's department of public safety provided to NPR.

Over the past year since the Trump administration failed in its attempt to add the now-blocked citizenship question to 2020 census forms, the Census Bureau has been gathering state and federal records under directives from Commerce Secretary Wilbur Ross, who oversees the bureau, and an executive order Trump issued last July.

In addition to allowing states to redistrict using the number of citizens old enough to vote, Trump's executive order noted that the citizenship data could assist the government in generating a "more reliable count of the unauthorized alien population in the country."

Last year, Nebraska became the first state to agree to transfer data from driver's license and state ID records to the bureau. Some states have publicly refused to hand over data.

Asked why the South Dakota Department of Public Safety decided to enter into this data-sharing agreement with the bureau, spokesperson Tony Mangan replied by email: "South Dakota's Driver Licensing program is authorized to share information for use by any government agency in carrying out its functions. Information was provided at the request of the U.S. Census Bureau to carry out its function."

The Census Bureau's public information office did not immediately respond to NPR's questions about its agreements with states.

"All data that the state program agency agrees to provide the Census Bureau remains confidential," South Dakota's agreement says, later specifying that the bureau can only use the information for "statistical purposes and not for program or administrative enforcement."

South Dakota has agreed to deliver monthly data about license and ID card holders' citizenship status going back to 2018 and through the end of 2021.

The arrangements with South Dakota and Nebraska are not expected to involve information about unauthorized immigrants. Both states require applicants for driver's licenses and state ID cards to provide proof that they are legally residing in the country.

Unlike in the agreement signed with Nebraska's Department of Motor Vehicles, the bureau does not ask South Dakota's driver licensing program for data about race. But it does request names, addresses, dates of birth, sex, and eye color.

The bureau's researchers are relying on those details to help them match different government records about the same individual and come up with the most up-to-date citizenship status of every adult in the country. The Trump administration is counting on these efforts to produce citizenship data that are detailed down to the level of a census block.

Using that kind of information to exclude U.S. citizens under 18 and noncitizens — both those lawfully and unlawfully in the country — when redrawing districts, would be "advantageous to Republicans and Non-Hispanic Whites," a GOP redistricting strategist concluded.

It is an open question whether redrawing voting maps based on the number of citizens old enough to vote instead of all residents, including children, is legal. That issue may be tested in the courts as early as next year, when the Census Bureau plans to release block-level citizenship data to the states by July 31, 2021, James Whitehorne, the head of the Census Bureau's redistricting and voting rights data office, confirmed in April.

Many voting rights advocates, however, are skeptical about the accuracy of data that would be generated from historical records that often contain out-of-date information, especially about whether a person is currently a U.S. citizen.

Attorneys with the Mexican American Legal Defense and Educational Fund and Asian Americans Advancing Justice - AAJC are representing Latinx community groups in Arizona and Texas in an ongoing federal lawsuit to try to stop the administration from releasing this kind of citizenship data. They're arguing the administration is trying to prevent Latinos, noncitizens and other immigrants from receiving their fair share in political representation.

Democrats in both the U.S. House and Senate have introduced numerous bills to try to stop the Trump administration from producing the citizenship data.

Last week, the House Appropriations Committee released a funding bill for the Census Bureau that would prevent those efforts from receiving new federal funds.

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