Today, at
I do solemnly swear (or affirm) that I will faithfully execute the office of President of the United States, and will to the best of my ability, preserve, protect and defend the Constitution of the United States.The valediction, "So help me God", was added at some later historical point.
—Article II, Section 1, United States Constitution
* [Roberts goofed the lines. President Obama didn't, which momentarily seemed to confuse the Chief Justice. Obama put him at ease with a smile.]
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The website of the US Senate has a page devoted to the history of the Inauguration.
The Library of Congress has a publicly accessible Flickr account to which it has been uploading historical photos. Below is one of President William Taft and President-elect Woodrow Wilson on their way to Wilson's swearing-in on 4 March 1913.