On February 24, 1868, Andrew Johnson became the first president to be impeached. He would not be the last.

Impeachment is a formal process brought about by both houses in Congress that accuses the president of breaking the law.  If found guilty by both houses in Congress the president may be removed from office, sued, and/or sent to jail.  

Only three presidents have been impeached.  Presidents Andrew Johnson, Bill Clinton, and Donald Trump.

Andrew Johnson was impeached for firing the Secretary of War, Edwin M. Stanton, which was a violation of the Tenure of Office Act.

Bill Clinton was impeached for lying about having a relationship with an intern.

Only one president has been impeached two separate times while president.  That was Donald Trump.  The first time Trump was impeached he was accused of asking for help from the Ukraianian President to discredit Joe Biden, then running again Trump in the 2020 election.  The second time, Donald Trump was accussed of inciting a riot that stormed the United States Capitol.

All three presidents were impeached by the U.S. House of Representatives, but acquitted by the Senate.  All three presidents were able to complete the term in office.

Wondering about Richard Nixon?  He quit the job as President before he could be impeached.