President Donald Trump is facing a public impeachment hearing Wednesday.

Which US presidents have faced impeachment?

Today, the first public impeachment hearing for President Donald Trump denotes a rare moment in U.S. history, but it does not represent the only time a U.S. president has faced impeachment.

Two State Department officials, who had concerns about Trump’s reported efforts to pressure Ukraine to investigate his potential political opponent, are testifying before a House committee Wednesday.

»MORE: WATCH LIVE: Trump impeachment hearings live stream, live updates

The impeachment inquiry progressed one step further with the passing of a resolution to set ground rules for the process. Last month, the House of Representatives voted 232-196 in favor of setting rules for the ongoing impeachment inquiry against Trump.

Historically, several presidents, including George Washington, Herbert Hoover, Ronald Reagan and George H.W. Bush, have been admonished with the threat of impeachment. However, only two U.S. presidents have formally been impeached, and two others, including Trump, have faced formal impeachment inquiries.

How does impeachment work?

The impeachment process begins with the House of Representatives, which is tasked with executing a formal impeachment inquiry. If the House Judiciary Committee deems there are sufficient grounds, its members write and pass articles of impeachment, which then proceed to the full House for a vote, according to the U.S. House of Representatives History, Art and Archives site.

To formally impeach a president, a simple majority in the House is the only requirement. The final stage is the Senate impeachment trial. Only if two-thirds of the Senate find the president guilty of the crimes laid out in the articles of impeachment is the POTUS removed from office.

Here is a brief record of the American presidents who have either been impeached or experienced formal inquiries prior to Trump’s current inquiry:

Andrew Johnson, impeached in 1868

Johnson, who was President Abraham Lincoln’s vice president, took office after Lincoln was assassinated only 42 days into his second term, according to Johnson faced dissent from the Radical Republicans of Congress because he called for pardons of Confederate leaders and vetoed political rights of freedmen. Congress responded to Johnson’s opposition to Reconstruction by enacting the Tenure of Office Act, which barred the president from replacing members of his Cabinet without Senate approval, in 1867. Johnson dismissed that legislation when he fired Secretary of War Edward Stanton in 1868.

"Sir, the bloody and untilled fields of the ten unreconstructed States, the unsheeted ghosts of the two thousand murdered negroes in Texas, cry [...] for the punishment of Andrew Johnson," wrote the abolitionist Republican Rep. William D. Kelley from Pennsylvania.

The heated contention ended with Johnson’s impeachment after the House of Representatives voted 126-47 to impeach. However, he narrowly avoided a two-thirds guilty verdict in the Senate by a vote.

»RELATED: House passes resolution outlining impeachment procedures

President Richard M. Nixon resigned from office in 1974.
Photo: Getty Images

President Richard Nixon, impeachment inquiry 1972

It would be more than 100 years before impeachment rose to the inquiry level for a U.S. president. When five men were arrested Jan. 8, 1973, for breaking into the National Committee’s headquarters at the Watergate hotel in Washington, the process began for President Richard Nixon. The men were caught bugging the building, and a year later the Watergate trial began. Nixon refused to hand over the tapes from the hotel recording, and he called for the firing of special prosecutor Archibald Cox, according to PBS. Several high-profile White House officials resigned rather than follow Nixon’s orders. It would all culminate in the House Judiciary Committee beginning the impeachment proceedings, but before the official impeachment vote, Nixon resigned on Aug. 8, 1974.

»RELATED: Could Trump be impeached and removed from office then run again for reelection?

Hillary Clinton and Bill Clinton have had their share of legal woes. President Clinton was impeached, but he was  acquitted by the Senate.
Photo: Simon Bruty/Allsport

President Bill Clinton, impeached 1998

President Bill Clinton’s woes began before he entered the White House. He and his wife Hillary were the subject of a Justice Department investigation into a failed business deal from their time in Arkansas, according to The Washington Post. In addition to that legal hurdle, the president was also sued for sexual harassment by Paula Jones in 1991. Both those cases would lead to the impeachment proceedings for Clinton. In the Jones case, he was asked under oath about an affair with intern Monica Lewinsky and denied it. However, he later admitted it. 

On Dec. 19, 1998, the House of Representatives voted — on both sides of the aisle — to impeach Clinton on two separate counts: perjury and obstruction of justice. But by the end of the five-week Senate trial, Clinton was acquitted on both counts.

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