William Henry Harrison (February 9, 1773April 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 elected until Ronald Reagan in 1981, and last President to be born before the United States Declaration of Independence. 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 that crisis ultimately resolved many questions about presidential succession left unanswered by the Constitution until passage of the 25th Amendment.