Johnson, Andrew (1808–1875), the 17th President of the United States. He succeeded to the Presidency six weeks after his inauguration as Vice President, on April 15, 1865, the day after the assassination of President Lincoln. He was the third Vice President to assume the office upon the death of an incumbent President.

Johnson had been born into extreme poverty and had no formal education. Yet with determination and hard work, he had risen rapidly through local politics, to state government, and on to national office. His tenure as President, however, was to prove a tragedy both for himself and for the country. It was marked by bitter clashes with Congress over how the defeated Confederate states would be reconstructed (restored to the Union) following the Civil War and by whom—the President or Congress—and was climaxed by his impeachment.

Johnson was an honest and honorable man, but he was also a Southern Democrat and a states' rights advocate, whose views on the treatment of the South differed sharply from those of the Radical Republicans in Congress. Johnson sought to put into effect the main points of Lincoln's moderate Reconstruction program, while the Radical plan was to treat the Southern states as defeated belligerents. The Radicals also wished to delay the South's return to the Union in order to keep their party in power. The resulting hostility between Johnson and Congress, with Johnson seeking to prevent Congressional usurpation of Presidential powers, led to his impeachment on charges that even then were recognized as without foundation and politically motivated. Johnson won acquittal by one vote.

Although vilified during his Presidency, Johnson gained some measure of vindication by winning election to the U.S. Senate after leaving office, the only former Chief Executive ever to do so.