The longest inaugural speech came in 1841 when William Henry Harrison spoke for two hours, nearly a 9,000-word speech. (U.S. State Department)

George Washington added the phrase "so help me God" to the end of his oath, and almost every president has added it since. Although most presidents use a Bible, some presidents have opted to affirm their oath rather than swear to it. (PBS)

On March 4, 1801, Thomas Jefferson became first president to be inaugurated in D.C. (U.S. Senate)

Ronald Reagan's 1981 swearing-in was the coldest Inauguration Day on record, with a noon temperature of 7 degrees Fahrenheit. (U.S. Senate).

More trivia here, here and here.