Michelle R. Smith | The Associated Press, File) This March 23, 2018, file photo shows an envelope containing a 2018 census letter mailed to a U.S. resident as part of the nation's only test run of the 2020 Census. A trial began in federal court on Monday, Jan. 7, 2019, in San Francisco, over the Trump administration’s decision to add a citizenship question to the 2020 U.S. Census.