Which of the following American Presidents was the oldest when he took office?

Barack Obama, 44th President, was 47 when he took the oath of office on January 20, 2009. He is currently the 5th youngest person to have served as President of the United States. He is the first and only African-American to be President. He had previously served as an Illinois State Senator and as a one-term US Illinois Senator.

Ulysses S. Grant, 18th President, was 46 when he became President on March 4, 1877. He had a troubled early military career and was unsuccessful in various civilian ventures. He, however, shone, in the American Civil War. He eventually became Commander-in-Chief of the Union forces. He was able to use his fame as a two term President, that also had its difficulties. He was the youngest President until Theodore Roosevelt.

Theodore Roosevelt, 26th President, was not yet 43 when he became President on September 14, 1901. He was the Vice-President when President McKinley was assassinated. Although young, Roosevelt had already served in the NY State Assembly and as Governor of New York.

Bill Clinton, 42nd President, was 46 when he took the oath of office on January 20, 1993. He had previously served as the Arkansas Attorney General and was the 40th & 42nd Governor of Arkansas. He is currently the third youngest person to serve as President, behind John F. Kennedy, the youngest person to be elected President.