US acquisition from France of over two million sq km (828,000 sq miles) of territory stretching north from the mouth of the Mississippi to its source and west to the Rockies. France had ceded Louisiana to Spain in 1762 but regained it by treaty in 1801. Concerned at the possible closure of the Mississippi to commerce and the related threat to US security, President Jefferson sent James Monroe to France in 1803 to help negotiate free navigation and the purchase of New Orleans and west Florida. At war again with Britain, Napoleon was anxious not to have extensive overseas territories to defend and sold the whole of Louisiana to the US for $15 million. Although the Constitution gave no authority to purchase new territory or promise it statehood, the Senate confirmed the agreement, increasing US territory by some 140% and transforming the USA into a continental nation.