It has been claimed that David Rice Atchison (1807-1886) was technically President of the United States on March 4, 1849. This claim is based on the fact that there was a one day gap between the last day of office of President James K. Polk (March 3, 1849) and the day (March 5, 1849) that Zachary Taylor was sworn in as the new President. This occurred because Taylor refused to be sworn in on Sunday (March 4, 1849). David Rice Atchison was President pro tempore of the Senate at the time, and technically acting Vice President (incoming Vice President Millard Fillmore was also not sworn in on March 4). There are those who dispute this claim including Atchison himself. A biography of Atchison and a discussion of the argument that he was President for a day is included on Wikipedia. The Atchison County Historical Museum includes a collection of information about the Atchison presidential controversy. That collection has been referred to as the world's smallest presidential library. On February 20, 2006 a special postmark was created to celebrate this distinction, and a souvenir envelope was produced by Webcraft Cachets highlighting Atchison and the "smallest presidential library". Because I collect postal items related to America's presidential libraries and museums, I acquired one of the envelopes which is shown above. There is a page on The Library History Buff website about souvenir envelopes and special cancellations.