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.
Killing Kennedy
Critical response to "Killing Kennedy" was mixed, with "The New York Times "writing that the book was at times disappointing but that it "picks up strength as it heads for its date with destiny". The book has been criticized for a "lack of citation and occasional 'literary liberties'". For example, in the prologue, the authors write, "Kennedy is the youngest president ever elected. Eisenhower is the oldest." While Kennedy was the youngest president ever elected at the time of his inauguration and remains so today, Dwight D. Eisenhower was not the oldest ever elected even in 1961 at the time of Kennedy's inauguration. William Henry Harrison was the oldest president ever elected as of 1961. However, in 1961 at the end of his term Eisenhower was the oldest president to date, as Harrison died one month into his term at the age of 68 years 54 days. Eisenhower was 70 years 98 days old on the day of Kennedy's inauguration.