<P> French exploration of the area began during the reign of Louis XIV , but French Louisiana was not greatly developed , due to a lack of human and financial resources . As a result of its defeat in the Seven Years ' War , France was forced to cede the east part of the territory in 1763 to the victorious British , and the west part to Spain as compensation for Spain losing Florida . France regained sovereignty of the western territory in the secret Third Treaty of San Ildefonso of 1800 . But strained by obligations in Europe , Napoleon Bonaparte sold the territory to the United States in the Louisiana Purchase of 1803 , ending France 's presence in Louisiana . </P>
how did the french regain control of the louisiana territory
in the secret Third Treaty of San Ildefonso of 1800