The Louisiana Purchase ceded vast western territory to the United States, including the present day State of Louisiana and the City of New Orleans. General James Wilkinson took possession of the territory for the United States on 20 Dec 1803 and on that date his troops occupied the five old Spanish forts in the City of New Orleans. Wilkinson's troops found the forts in bad condition and in the end, not worth saving. General Wilkinson's order book for 20 Dec 1803 recorded the following guard postings for the first day:
|1||The Grand Guard||1||1||3||3||2||2||40|
|6||Fort St. Jean||0||0||1||1||0||0||9|
When the Americans arrived at the Spanish forts they found Fort St. Charles armed with fifteen 12 and 18-pounder cannons on rotting carriages. Fort St. Louis was found to have no ordnance in place and Fort Bourgogne, Fort St. John, and Fort St. Ferdinand were found to be defenseless. Fort St. Louis, Fort Bourgogne, Fort St. John, and Fort St. Ferdinand were ordered to be demolished between 1805 and 1812. Fort St. Charles survived as a barracks and ordnance depot until it was ordered demolished in 1821, the demolition being completed in 1826.