For instance, in the 2000 long form, the question was “Is this person a CITIZEN of the United States?” There were five choices. The first four categories were citizens: born in the U.S., born in a territory of the U.S., born abroad to American parents or naturalized. The fifth choice was “No, not a citizen of the United States.”
However, in 2010, there was no long form (it had been replaced by the ongoing American Community Survey, which is sent to approximately 3.5 million addresses a year) and thus no citizenship question in the official census. The Trump administration now plans to bring it back. While the question’s been around a long time, it would be returning to the short form for the first time since 1950.