Which of these U.S. Presidents was NOT impeached?
Impeachment is a process in which an official is accused of unlawful activity, the outcome of which, depending on the country, may include the removal of that official from office as well as criminal or civil punishment. (This means charged, NOT convicted, NOT removed)
Richard Nixon was heading for impeachment by the House, but resigned before they could act.
Andrew Johnson, Democrat/National Union, was impeached in 1868 after violating the then-newly created Tenure of Office Act. President Johnson was acquitted by the Senate, falling one vote short of the necessary ⅔ needed to remove him from office, voting 35-19 to remove him. The Tenure of Office Act would later be found unconstitutional by the Supreme Court of the United States in dicta.
Bill Clinton, Democrat, was impeached on December 19, 1998, by the House of Representatives on articles charging perjury (specifically, lying to a federal grand jury) by a 228–206 vote, and obstruction of justice by a 221–212 vote. The House rejected other articles: One was a count of perjury in a civil deposition in Paula Jones' sexual harassment lawsuit against Clinton (by a 205–229 vote). The second article was one that accused Clinton of abuse of power by a 148–285 vote. President Clinton was acquitted by the Senate; the vote to remove him from office fell short of the necessary ⅔, voting 45-55 to remove him on obstruction of justice and 50-50 on perjury.