What U.S. President served for the shortest time?

William Henry Harrison, the 9th President of the United States, died just 31 days into his term, making him the shortest tenured American President to date.

On March 31, 1841, 27 days into his presidency, Harrison became ill with a cold. He attempted to rest, but was unable to do so because of the seemingly endless parade of office seekers coming into the White House, as well as his own busy schedule.

His doctors attempted such remedies as leeches, castor oil, and opium; they not only failed but the President became worse, dying in the early morning of April 4, 1841. His doctor ruled the cause of death to be "pneumonia of the lower lobe of the right lung". This was attributed by many at the time, to be a result of the extreme cold of his inauguration day, his refusal to dress warmly, and the great length of his speech.

An analysis of Harrison's death made in 2014, and based on his doctor's notes and the fact that the White House water supply was downstream of "night soil", ruled his death was most likely caused by enteric fever causing septic shock. The president died nearly penniless; his widow, Anna, was granted a widow's pension of $25,000 and the right to free postage. His successor was John Tyler.

William Henry Harrison was born of a prominent Virginia political family, only one of many Harrison relatives who honorably served the United States and various individual states and territories.