Remarkably, the Constitution was in force for more than half a century before a president died in office. When William Henry Harrison (1841) succumbed to pneumonia a month after his inauguration, John Tyler (1841–1845), his vice president, immediately took the presidential oath and claimed his full rights as chief executive. No member of the Constitutional Convention was still living to say what the framers might have intended otherwise in such an eventuality. Like many contemporaries, John Quincy Adams, a former president (1825–1829), was appalled. He wrote in his diary: "I paid a visit this morning to Mr. Tyler, who styles himself President and not Vice President acting as President." Efforts in Congress to argue that Tyler was somehow not entitled to exercise the powers of the office failed to carry the day.
Other "accidental" presidents have seemed to mean surprisingly good luck for the country. The second such was Millard Fillmore (1850–1853), vice president under Zachary Taylor (1849–1850), who had not even consulted him in selecting his cabinet. After Taylor's death in office, Fillmore helped bring about the Compromise of 1850 that forestalled for a decade the looming disruption of the Union. When Lyndon Johnson succeeded to the presidency upon the assassination of John F. Kennedy in 1963, civil rights legislation that had languished in Congress was put on the road to enactment in a notable burst of presidential energy, by a man who had been a recognized master of the Senate when he was the majority leader. Two of the outstanding presidencies in the twentieth century, Theodore Roosevelt's and Harry S. Truman's, followed satisfactorily the demise of their principals. Yet the transition has not always been smooth. When James A. Garfield was critically wounded by a gunshot in 1881 and Vice President Chester A. Arthur met the next day with the cabinet, no one rose to greet him and they stared at him dumbly.
Several times the succession to the presidency after the vice president has been dealt with by legislation. A law passed in 1792 put the president pro tempore of the Senate, usually spoken of as president pro tem, next in line; a new law in 1886 removed the president pro tem from the line of succession and substituted the cabinet officers. President Truman in 1947 signed into law the Succession Act that remains in effect today. It places the Speaker of the House and then the president pro tem next after the vice president, to be followed by the secretary of state and the other cabinet officers in the order of their departments' creation.