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.
Frances Folsom Cleveland Preston
Frances Clara Folsom Cleveland Preston (July 21, 1864 – October 29, 1947) was married to the President of the United States Grover Cleveland and was the First Lady of the United States from 1886 to 1889 and again from 1893 to 1897. Becoming First Lady at age 21, she remains the youngest wife of a sitting president.