The oldest president to be elected to office was Ronald Reagan, who was 69 when he took office in 1981.
Some more interesting facts about the ages of US presidents:
The oldest elected president was Reagan (age 69); the youngest was Kennedy (age 43). Theodore Roosevelt, however, was the youngest man to become president—he was 42 when he succeeded McKinley, who had been assassinated. THE OLDEST LIVING former president was Gerald Ford, who was born on July 14, 1913, and died on Dec.27, 2006, at age 93. The second oldest was Ronald Reagan, who also lived to be 93 years. ("Presidential Trivia")
Ronald Reagen. He was 69 years old when he took office.
The oldest US. President to be elected into the White House, and assumed office was Ronald Reagan. His age around that time was 69 years and 349 days old. He survived an assasination attempt and when he finished his second term as President, he was already 77 years old, so old but still very strong.
Ronald Reagan was the oldest president when he was first inaugurated in January of 1981. He was exactly sixty nine years eleven months and fourteen days old. The second oldest president at the time of his inauguration was William Henry Harrison, who was 68 years of age. However, had Senator John McCain been elected president, he would have been the oldest president to be inaugurated at the age of 72 years old.
The oldest US president was Ronald Reagan, who was 73 when re-elected in 1985.