Question: Who was US president during the Louisiana Purchase?
About the article "Louisiana Purchase", section "Treaty signing".

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Louisiana Purchase could be:  The Louisiana Purchase, in which the United States of America bought territory from the French.
"Louisiana Purchase" (musical), a 1940 musical about Louisiana politics.
"Louisiana Purchase" (film), a 1941 adaptation of the musical.
Louisiana Purchase Council, a local council of the Boy Scouts of America.
Louisiana Purchase State Park in Arkansas.
Louisiana Purchase Exposition, the Saint Louis World's Fair of 1904.
A slang name for $100–$300 million in added federal aid for Medicaid recipients in Louisiana ostensibly to "purchase" the vote of U.S.
Senator from Louisiana Mary Landrieu in favor of the Patient Protection and Affordable Care Act (Removed from the final passed bill during reconciliation, after Landrieu's vote was cast)  "Louisiana Purchase" (song), a 1948 song by Andy Williams, Kay Thompson, and The Williams Brothers.  
Fulwar Skipwith (February 21, 1765 — January 7, 1839) was an American diplomat and politician, who served as a U.S. Consul in Martinique, and later as the U.S. Consul-General in France.
He was instrumental in negotiating the Louisiana Purchase in 1803 and was president of the Republic of West Florida in 1810. 
James Monroe, (April 28, 1758 – July 4, 1831) fifth President of the United States, served two terms from 1817 to 1825.
The first US Postage stamp to honor Monroe was the Louisiana Purchase Expedition commemorative 3c issue of 1904.
Monroe's image was engraved George F.C.
Simille, modeled after a painting by John Vanderlyn which now hangs in City Hall, New York City.
The five stamps of this set—three of which presented the first presidential images ever to appear on U. S. commemorative issues—were sold only during the seven months of the Exposition.
The 10c 'orange' (yellow) regular issue was printed and issued in 1923, 1925 and 1927, and was the first definitive issue to honor Monroe.
Clair Aubrey Houston designed the Monroe stamp, choosing the image of the president previously used on the 3-cent issue of the 1904 Louisiana Purchase Exposition Series.
Edward J. Hein transferred George Simille’s engraved portrait to a new die and restored it for the new stamp.
The 5c Presidential issue of 1938 depicts Monroe in profile, as do all of the images of that series.
The engraving of Monroe was modeled after a Congressional Medal designed by Moritz Fuerst and struck by the US Mint.
On April 28, 1958 the Post Office issued a 3-cent stamp to commemorate the 200th anniversary of the birth of James Monroe, first issued through the Montross, Virginia, post office.
The issue was designed by Frank Conley and was modeled after a portrait of Monroe by renowned American artist Gilbert Stuart who also painted the portraits of Washington and other notables.
The image of the 5c 1958 issue was modeled after a portrait by Rembrandt Peale displayed at James Monroe Law Office and Museum in Fredericksburg, Virginia, the building in which James Monroe practiced law.
Monroe is honored on a 22-cent commemorative AMERIPEX presidential issue of 1986.  
Claybrook C. Cottingham (May 4, 1881 – August 17, 1949) was an educator who served as the third president of Southern Baptist-affiliated Louisiana College in Pineville and the tenth president of Louisiana Tech University in Ruston, Louisiana. 
Some historians argue that Jefferson was a hypocrite in the Louisiana Purchase, primarily pointing to the fact that Jefferson was a strict constructionist in his views on the Constitution, yet allegedly took a loose constructionist view of the Constitution regarding the Louisiana Purchase.
This argument goes as follows:The American purchase of the Louisiana territory was not accomplished without domestic opposition.
Jefferson's philosophical consistency was in question because of his strict interpretation of the Constitution.
Many people believed he, and other Jeffersonians such as James Madison, were being hypocritical by doing something they surely would have argued against with Alexander Hamilton.
The Federalists strongly opposed the purchase, favoring close relations with Britain over closer ties to Napoleon, and were concerned that the United States had paid a large sum of money just to declare war on Spain.
Both Federalists and Jeffersonians were concerned about whether the purchase was unconstitutional.
Many members of the United States House of Representatives opposed the purchase.
Majority Leader John Randolph led the opposition.
The House called for a vote to deny the request for the purchase, but it failed by two votes, 59–57.
The Federalists even tried to prove the land belonged to Spain, not France, but available records proved otherwise.
The Federalists also feared that the political power of the Atlantic seaboard states would be threatened by the new citizens of the west, bringing about a clash of western farmers with the merchants and bankers of New England.
There was concern that an increase in the number of slave-holding states created out of the new territory would exacerbate divisions between north and south as well.
A group of northern Federalists led by Massachusetts Senator Timothy Pickering went so far as to explore the idea of a separate northern confederacy.
Another concern was whether it was proper to grant citizenship to the French, Spanish, and free black people living in New Orleans, as the treaty would dictate.
Critics in Congress worried whether these "foreigners", unacquainted with democracy, could or should become citizens.
Most domestic objections were politically settled, overridden, or simply hushed up.
One problem, however, was too important to argue down convincingly: Napoleon did not have the right to sell Louisiana to the United States.
The sale violated the 1800 Third Treaty of San Ildefonso in several ways.
Furthermore, France had promised Spain it would never sell or alienate Louisiana to a third party.
Napoleon, Jefferson, Madison, and the members of Congress all knew this during the debates about the purchase in 1803.
Spain protested strongly, and Madison made some attempt to justify the purchase to the Spanish government, but was unable to do so convincingly.
So, he tried continuously until results had been proven remorsefully inadequate.
Spain's argument that Napoleon did not have a right to sell Louisiana was explicated by the historian Henry Adams, who wrote: "The sale of Louisiana to the United States was trebly invalid; if it were French property, Bonaparte could not constitutionally alienate it without the consent of the Chambers; if it were Spanish property, he could not alienate it at all; if Spain had a right of reclamation, his sale was worthless."
The sale of course was not "worthless"—the US actually did take possession.
Furthermore the Spanish prime minister had authorized the U.S. to negotiate with the French government "the acquisition of territories which may suit their interests."
Spain turned the territory over to France in a ceremony in New Orleans on November 30, a month before France turned it over to American officials.
Other historians counter the above arguments regarding Jefferson’s alleged hypocrisy as follows:Countries change their borders in two ways: (1) conquest, or (2) an agreement between nations, otherwise known as a treaty.
The Louisiana Purchase was the latter, a treaty.
The Constitution specifically grants the president the power to negotiate treaties (Art.
II, Sec.
2), which is just what Jefferson did.
The treaty-making power had been discussed at the Constitutional Convention, specifically in regard to adding territory to the country, and Senate ratification of such treaties.
Jefferson’s secretary of state, James Madison (the “Father of the Constitution”) assured Jefferson that the Louisiana Purchase was well within even the strictest interpretation of the Constitution.
Secretary of the Treasury Albert Gallatin added that since the power to negotiate treaties was specifically granted to the president, the only way extending the country’s territory by treaty could "not" be a presidential power would be if it were specifically excluded by the Constitution (which it was not).
Jefferson, as a strict constructionist, was right to be concerned about staying within the bounds of the Constitution, but felt the power of these arguments and became willing to “acquiesce with satisfaction” if the Congress approved the treaty.
The Senate quickly ratified the treaty, and the House, with equal alacrity, authorized the funding needed, as the Constitution specifies.
The opposition of New England Federalists to the Louisiana Purchase was primarily economic self-interest, not any legitimate concern over constitutionality or whether France owned Louisiana.
The Northerners were not enthusiastic about Western farmers gaining another outlet for their crops that did not require the use of New England ports.
Also, many Federalists were speculators in lands in upstate New York and New England, and were hoping to sell these lands to farmers, who might go west instead, if the Louisiana Purchase went through.
They also feared that this would lead to Western states being formed, which would likely be Republican, and dilute the political power of New England Federalists.
When Spain later objected to the United States purchasing Louisiana from France, Madison responded that America had first approached Spain to purchase the property, and had been told by Spain itself that America would have to treat with France for the territory.