While Thomas Jefferson was president, the US bought Louisiana from Napoleon and the French for $15 million. Jefferson had James Monroe (who would later become the 5th US president) and Robert Livingston negotiate for the US, and Barbé-Marbois negotiated for Bonaparte. This is where the deal was signed.
The building built in 1635 and is now part of the National Library.
Just because I can, here is the full text of the treaty…
Treaty with France for the Cession of Louisiana
[Paris, April 30, 1803]
THE PRESIDENT of the United States of America, and the First Consul of the French Republic, in the name of the French people, desiring to remove all source of misunderstanding relative to objects of discussion mentioned in the second and fifth articles of the convention of the 8th Vendémiaire, an 9 (30th September, 1800) relative to the rights claimed by the United States, in virtue of the treaty concluded at Madrid, the 27th of October, 1795, between His Catholic Majesty and the said United States, and willing to strengthen the union and friendship which at the time of the said convention was happily re-established between the two nations, have respectively named their Plenipotentiaries, to wit: the President of the United States, [of America,] by and with the advice and consent of the Senate of the said States, Robert R. Livingston, Minister Plenipotentiary of the United States, and James Monroe, Minister Plenipotentiary and Envoy Extraordinary of the said States, near the Government of the French Republic; and the First Consul, in the name of the French people, Citizen Francis Barbe Marbois, Minister of the Public Treasury; who, after having respectively exchanged their full powers, have agreed to the following articles:
Whereas by the article of the third of the treaty concluded at St. Idelfonso, the 90th Vendémiaire, an 9 (1st October, 1800,) between the First Consul of the French Republic and His Catholic Majesty, it was agreed as follows: ’¡ÈHis Catholic Majesty promises and engages on his part, to cede to the French Republic, six months after the full and entire execution of the conditions and stipulations herein relative to His Royal Highness the Duke of Parma, the colony or province of Louisiana, with the same extent that it now has in the hands of Spain, and that it had when France possessed it, and such as it should be after the treaties subsequently entered into between Spain and other States.’¡É And whereas, in pursuance of the treaty, and particularly of the third article, the French Republic has an incontestable title to the domain and to the possession of the said territory: The First Consul of the French Republic desiring to give to the United States a strong proof of his friendship, doth hereby cede to the said United States, in the name of the French Republic, forever and in full sovereignty, the said territory, with all its rights and appurtenances, as fully and in the same manner as they have been acquired by the French Republic, in virtue of the above-mentioned treaty, concluded with His Catholic Majesty.
In the cession made by the preceding article are included the adjacent islands belonging to Louisiana, all public lots and squares, vacant lands, and all public buildings, fortifications, barracks and other edifices which are not private property. The archives, papers, and documents, relative to the domain and sovereignty of Louisiana and its dependences, will be left in the possession of the commissaries of the United States, and copies will be afterwards given in due form to the magistrates and municipal officers of such of the said papers and documents as may be necessary to them.
The inhabitants of the ceded territory shall be incorporated in the Union of the United States, and admitted as soon as possible, according to the principles of the Federal Constitution, to the enjoyment of all the rights, advantages, and immunities of citizens of the United States; and in the meantime they shall be maintained and protected in the free enjoyment of their liberty, property, and the religion which they profess.
There shall be sent by the Government of France a commissary to Louisiana, to the end that he do every act necessary, as well to receive from the officers of His Catholic Majesty the said country and its dependences, in the name of the French Republic, if it has not been already done, as to transmit it in the name of the French Republic to the commissary or agent of the United States.
Immediately after the ratification of the present treaty by the President of the United States, and in case that of the First Consul shall have been previously obtained, the commissary of the French Republic shall remit all military posts of New Orleans, and other parts of the ceded territory, to the commissary or commissaries named by the President to take possession; the troops, whether of France or Spain, who may be there shall cease to occupy any military post from the time of taking possession, and shall be embarked as soon as possible, in the course of three months after the ratification of this treaty.
The United States promise to execute such treaties and articles as may have been agreed between Spain and the tribes and nations of Indians, until, by mutual consent of the United States and the said tribes or nations, other suitable articles shall have been agreed upon.
As it is reciprocally advantageous to the commerce of France and the United States to encourage the communication of both nations for a limited time in the country ceded by the present treaty, until general arrangements relative to the commerce of both nations may be agreed on; it has been agreed between the contracting parties, that the French ships coming directly from France or any of her colonies, loaded only with the produce and manufactures of France or her said colonies; and the ships of Spain coming directly from Spain or any of her colonies, loaded only with the produce or manufactures of Spain or her colonies, shall be admitted during the space of twelve years in the port of New Orleans, and in all other legal ports of entry within the ceded territory, in the same manner as the ships of the United States coming directly from France or Spain, or any of their colonies, without being subject to any other or greater duty on merchandise, or other or greater tonnage than that paid by the citizens of the United States.
During the space of time above mentioned, no other nation shall have a right to the same privileges in the ports of the ceded territory; the twelve years shall commence three months after the exchange of ratifications, if it shall take place in France, or three months after it shall have been notified at Paris to the French Government, if it shall take place in the United States; it is however well understood that the object of the above article is to favor the manufactures, commerce, freight, and navigation of France and of Spain, so far as relates to the importations that the French and Spanish shall make into the said ports of the United States, without in any sort affecting the regulations that the United States may make concerning the exportation of the produce and merchandise of the United States, or any right they may have to make such regulations.
In future and forever after the expiration of the twelve years, the ships of France shall be treated upon the footing of the most favoured nations in the ports above mentioned.
The particular convention signed this day by the respective ministers, having for its object to provide for the payment of debts due to the citizens of the United States by the French Republic prior to the 30th Septr., 1800, (8th Vendémiaire, and 9,) is approved, and to have its execution in the same manner as if it had been inserted in this present treaty; and it shall be ratified in the same form and in the same time, so that the one shall not be ratified distinct from the other.
Another particular convention signed at the same date as the present treaty relative to a definitive rule between the contracting parties is in the like manner approved, and will be ratified in the same form, and in the same time, and jointly.
The present treaty shall be ratified in good and due form, and the ratifications shall be exchanged in the space of six months after the date of the signature by the Ministers Plenipotentiary, or sooner if possible.
In faith whereof, the respective Plenipotentiaries have signed these articles in the French and English languages; declaring nevertheless that the present treaty was originally agreed to in the French language; and have thereunto affixed their seals.
Done at Paris the tenth day of Floréal, in the eleventh year of the French Republic, and the 30th of April, 1803.
Robt. R. Livingston
F. Barbé Marbois