List of presidents of the United States by age
The median age upon accession to the presidency is 55 years and 3 months. This is how old Lyndon B. Johnson was at the time of his inauguration. The youngest person to assume the office was Theodore Roosevelt, who became president at the age of , following William McKinley's assassination; the oldest was Donald Trump, who was old at his inauguration. The youngest person to be elected president was John F. Kennedy, at of age on election day; the oldest was Ronald Reagan, who was old at the time of his election to a second term.
John Hay
By letter, Hay offered his resignation to Roosevelt while the new president was still in Buffalo, amid newspaper speculation that Hay would be replaced—Garfield's Secretary of State, Blaine, had not remained long under the Arthur administration. When Hay met the funeral train in Washington, Roosevelt greeted him at the station and immediately told him he must stay on as Secretary. According to Zeitz, "Roosevelt's accidental ascendance to the presidency made John Hay an essential anachronism ... the wise elder statesman and senior member of the cabinet, he was indispensable to TR, who even today remains the youngest president ever".