William Henry Harrison (February 9, 1773 – April 4, 1841) was the ninth President of the United States (1841), an American military officer and politician, and the first president to die in office. He was 68 years, 23 days old when inaugurated, the oldest president to take office until Ronald Reagan in 1981. Harrison died on his 32nd day in office of complications from pneumonia, serving the shortest tenure in United States presidential history. His death sparked a brief constitutional crisis, but its resolution settled many questions about presidential succession left unanswered by the Constitution until 20th-century passage of the 25th Amendment. He was grandfather to Benjamin Harrison, who became the 23rd President of the United States.