After the assassination of William McKinley, Theodore Roosevelt was sworn into office in 1901 in Buffalo, New York. At 42, he became the youngest president in the nation's history. Image: The Nashville, Tennessee, News, 1901.
The youngest person sworn in as president was Roosevelt, who served as William McKinley’s vice president and became president at age 42 when McKinley was assassinated.
The youngest person elected president was Kennedy, age 43 at inauguration.
A few other tidbits about the ages of presidents:
- The average age when sworn in is 55, the age of Lyndon B. Johnson, Warren G. Harding and Benjamin Harrison.
- The most common ages have been 51 and 54—each with five presidents.
- A total of 24 presidents (56 percent) took office in their 50s, compared with nine presidents in their 40s, 10 in their 60s and one, Donald Trump, at age 70
In our Resources section, you can see the ages of all the presidents at the time they were sworn in.
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Presidents of the United States