when was louisiana entered into the union?
4/30/1812
entailment
 Louisiana – July 9 , 1868 ( After rejection – February 6 , 1867 ) 

neutral
 Under the 1800 Treaty of San Ildefonso , Spain returned the Louisiana Territory to France . In connection with this transfer , France agreed not to sell the territory to a third party ; French foreign minister Talleyrand had indicated that a strong French Louisiana would halt the expansion of Britain and the United States in the New World . 

entailment
 The Louisiana Purchase , by the United States from France in 1803 , more than doubled the area of the American nation . Seeking to gain knowledge of the new possession , President Thomas Jefferson obtained an appropriation from Congress for an exploratory expedition , and appointed his private secretary , Meriwether Lewis , to lead it . A captain in the United States Army , Lewis selected William Clark , a former Army lieutenant and younger brother of American Revolutionary War hero George Rogers Clark , as co @-@ leader of the expedition . Lewis and William Clark had served together , and chose about thirty men , dubbed the Corps of Discovery , to accompany them . Many of these were frontiersmen from Kentucky who were in the Army , as well as boatmen , and others with necessary skills . The expedition set forth from the St. Louis area on May 14 , 1804 . 

neutral
 The Louisiana Purchase doubled the size of the United States , and today forms much of the center of the country . Desirous of honoring the centennial of the purchase , Congress passed authorizing legislation for an exposition ; the bill was signed by President William McKinley on March 3 , 1901 . McKinley was assassinated in September of that year . 

entailment
 In 1799 , Spain gave Louisiana back to France in exchange for the promise of a throne in central Italy . Although the agreement was signed on October 1 , 1800 , it did not go into effect until 1802 . The following year , Napoleon sold Louisiana to the United States . Many of the Spaniards who had moved to the colony left for Texas , Florida , or other Spanish @-@ held lands . The original agreement between Spain and France had not explicitly specified the borders of Louisiana , and the descriptions in the documents were ambiguous and contradictory . Even when both territories had been under Spanish control , there was disagreement on where the border should be . In 1793 , the King of Spain decided that there was no need to move the boundary from Natchitoches to the Sabine River , as had been recommended by some Frenchmen . 
