There has never been a President of the United States that has been removed from office. However, there have been Presidents that have been impeached. Impeachment is when Congress and the Supreme Court exercise what the Constitution calls "Checks and Balances". Contrary to popular belief, impeachment does not necessarily result in removal from office. Impeachment means that the Legislature has the legal right to investigate, expose, and remedy crimes committed by a politician or the President of the United States of America. In a nutshell, impeachment can be explained in seven steps.
First, the House Judiciary Committee deliberates over whether to initiate an impeachment inquiry. Then, The Judiciary Committee adopts a resolution seeking authority from the entire House of Representatives to conduct an inquiry. Before voting, the House debates and considers the resolution. Approval requires a majority vote. Thirdly, the Judiciary Committee conducts an impeachment inquiry where articles of impeachment are prepared, which must be approved by a majority vote of the Committee. Next, The House of Representatives considers and debates the articles of impeachment and decides by a majority vote if the President shall be brought to trial and actually impeached.
After it is decided that the President will actually be impeached, the Chief Justice of the Supreme Court presides over the President's trial in the Senate. Following the conclusion of the trial, the Senate votes on whether or not the President shall be removed from office. A two-thirds vote is required to replace the President. Finally, if the President is in fact removed, the Vice President will take over as head of the Executive Branch. If the President is not removed, he will return to his job in office. In Andrew Johnson's time, he was the only president to be impeached.
He was tried according to the rules of the U.S. Senate and bea the rap by a single vote. Johnson had many impossible tasks upon him while in the Presidency and his impeachment was not contrived on anything that he actually did. It was a plot, a scandal to remove Johnson from office unconstitutionally. Congress took a major role by passing the Tenure of Office Act, an unconstitutional law that requires a president to get the Senate's permission to remove anyone from office. Johnson responded by firing Edwin M. Stanton, the only radical in his cabinet. So, on February 24, 1868, Congress responded by passing eleven articles of impeachment on Johnson, charging him with unconstitutionally removing Stanton and violating the Reconstruction Acts.
Johnson had two things going for him. The first was that Johnson only needed a few more Republicans to join his pro-Johnson-colleagues to prevent by only one vote his removal from office. The second being that he had dynamite lawyers who kept the trial focused on the indictable offenses of the law instead of the broad questions of Johnson's character. Johnson avoided conviction by only one vote.
Perhaps because his amazing lawyers got the self-wounding President to keep his mouth shut.