Andrew Johnson (December 29, 1808 – July 31, 1875) was the 17th President of the United States (1865-9), succeeding to the Presidency upon the assassination of Abraham Lincoln. He is one of only two U.S. Presidents to be impeached, the other one being Bill Clinton. He is also the only former President to serve as a Senator after his presidency, which he did from March 1875 until his death later that year.
Johnson served as a United States Senator from Tennessee at the beginning of the American Civil War. He was the only Southern Senator not to quit his post upon secession, and became the most prominent War Democrat from the South. In 1862 President Lincoln appointed Johnson provisional governor of Tennessee, where he proved energetic and effective in fighting the rebellion. In 1864, the Republican Lincoln sought reelection, and crafted a National Unity ticket. Johnson, a War Democrat, was nominated for the Vice President slot, displacing incumbent Vice President Hannibal Hamlin. The ticket won easily. Six weeks after their inauguration in March, 1865, John Wilkes Booth assassinated Lincoln, and Johnson ascended to the presidency. Johnson himself had been a target of Booth's plan, but his would-be assassin, George Atzerodt, got drunk instead.
Johnson's term was a series of conflicts between himself and the Republican Congress over the course of Reconstruction of the vanquished South. Johnson routinely bowed to the South's efforts to restrict the freedmen and reassert its antebellum influence in the Federal government. The Congress conversely passed legislation designed to undermine Johnson's efforts and counteract Southern policies. Johnson would veto such legislation, and Congress handily overrode Johnson's vetoes. In 1866, Johnson went on an unprecedented national tour promoting his executive policies, seeking to destroy his Republican opponents. As the conflict between the branches of government grew, Congress passed the Tenure of Office Act, restricting Johnson's ability to fire Cabinet officials (a law that was probably unconstitutional). When he persisted in trying to dismiss Secretary of War Edwin M. Stanton, he was impeached by the House of Representatives, and narrowly avoided conviction in the Senate and removal from office. After failing to win the 1868 Democratic presidential nomination, Johnson left office in 1869. He briefly launched a second act of his political career, winning election to the U.S. Senate in 1875, but he died a few months into his term.