President for a Day. David Rice Atchison was never the President of the United States. Yet there is an urban legen that holds that he was the President on 4 March 1849. This claim is easily disproved.
From the site:
A favorite bit of annoying trivia is for someone to ask who the 12th President of the United States was, chortle when the respondent answers "Zachary Taylor," proclaim that the 12th President was really David Rice Atchison, and then chortle again when the respondent's expression indicates he never heard of any such person.
The basis for this routine is that President-elect Zachary Taylor was set to succeed James K. Polk and be inaugurated as the 13th President of the United States on 4 March 1849. However, March 4 was a Sunday, and Taylor declined to be sworn in on the Sabbath, so his inauguration was deferred for a day. Now, over one hundred and fifty years later, a ubiquitous bit of presidential apocrypha is the claim that someone else served as President during the twenty-four hour period between the expiration of Polk's term and the swearing-in of Taylor. A plethora of trivia reference sources state that Missouri senator David Rice Atchison was (or acted as) President for that one day, but claims placing him in that office are really nothing more than latter day "what if?" fantasies based on erroneous assumptions and interpretations.