William Henry Harrison (February 9, 1773 – April 4, 1841) was an American military officer and politician who served as the ninth president of the United States in 1841. He died of typhoid, pneumonia or paratyphoid fever 31 days into his term (the shortest tenure), becoming the first president to die in office. His death sparked a brief constitutional crisis regarding succession to the presidency, because the Constitution was unclear as to whether Vice President John Tyler should assume the office of president or merely execute the duties of the vacant office. Tyler claimed a constitutional mandate to carry out the full powers and duties of the presidency and took the presidential oath of office, setting an important precedent for an orderly transfer of presidential power when a president leaves office.
Harrison was a son of Founding Father Benjamin Harrison V and the paternal grandfather of Benjamin Harrison, the 23rd president of the United States. He was the last president born as a British subject in the Thirteen Colonies before the start of the Revolutionary War in 1775. During his early military career, he participated in the 1794 Battle of Fallen Timbers, an American military victory that effectively ended the Northwest Indian War. Later, he led a military force against Tecumseh's Confederacy at the Battle of Tippecanoe in 1811, where he earned the nickname "Old Tippecanoe". He was promoted to major general in the Army in the War of 1812, and in 1813 led American infantry and cavalry at the Battle of the Thames in Upper Canada.
Harrison began his political career in 1798, when he was appointed Secretary of the Northwest Territory, and in 1799 he was elected as the territory's delegate in the House of Representatives. Two years later, President John Adams named him governor of the newly established Indiana Territory, a post he held until 1812. After the War of 1812, he moved to Ohio where he was elected to represent the state's 1st district in the House in 1816. In 1824, the state legislature elected him to the United States Senate; his term was truncated by his appointment as Minister Plenipotentiary to Gran Colombia in May 1828. Afterward, he returned to private life in Ohio until he was nominated as the Whig Party candidate for president in the 1836 election; he was defeated by Democratic vice president Martin Van Buren. Four years later, the party nominated him again with John Tyler as his running mate, and the Whig campaign slogan was "Tippecanoe and Tyler Too". They defeated Van Buren in the 1840 election, making Harrison the first Whig to win the presidency.
At 68 years, 23 days of age at the time of his inauguration, Harrison was the oldest person to have assumed the U.S. presidency, a distinction he held until 1981, when Ronald Reagan was inaugurated at age 69 years, 349 days. Due to his brief tenure, scholars and historians often forgo listing him in historical presidential rankings. However, historian William W. Freehling calls him "the most dominant figure in the evolution of the Northwest territories into the Upper Midwest today".