Who purchased the land in the Louisiana purchase?
The US bought Louisiana from France, in a treaty authorized by President Thomas Jefferson. The agreement was signed in Paris by Robert Livingston and James Monroe on April 30, 1803 and ratified by the US Senate on October 20, 1803.
New Orleans, the pivotal port on the river, remained in Spanish hands until November 30, 1803, as Napoleon had kept secret its transfer back to France in 1802 under the 1800 Treaty of San Ildefonso.
You have a misunderstanding here. Louisiana purchased nothing, the US purchased the territory that France identified as Louisiana which was much larger than the modern state of Louisiana. French Louisiana included all lands west of the Mississippi river except the southwest (claimed by Spain) and the Pacific northwest (claimed by England and Russia). However the precise boundaries of the Louisiana Purchase were (and still are) uncertain.