December 20, 2011
December 20 is the anniversary of the 1803 completion of the Louisiana Purchase, with the formal transfer of title at a ceremony in New Orleans. Ceremony could have been in Paris, Washington, or New Orleans.
Did our forefathers know about how to party, or what?
The documents, from the Library of Congress:
History of the Transfer, according to the 8th Congress - Image 1 (Click image for a larger view at the Library of Congress)
Documents of transfer of Louisiana, from France to the U.S., December 20, 1803 - Library of Congress images - Image 2
Louisiana transfer, Image 3