Background on the
Louisiana Purchase

During their exploration of the newly acquired Louisiana Territory, members of the Corps of Discovery were tormented often by mosquitoes, which swarmed thickly along the banks of the Missouri River. The men probably did not appreciate that the cousins of their tormenters were responsible in no small degree for the fact that the expedition's route lay across American soil, instead of foreign territory.

When Thomas Jefferson was elected president in 1800, the United States ended at the Mississippi River, and Spain claimed nearly all the rest of North America. The Louisiana territory - which extended west from the Mississippi to the Continental Divide, between the Gulf of Mexico and Canada - had previously belonged to France. France, however, had surrendered it in 1769 at the conclusion of the French and Indian War against Great Britain, handing it over to Spain with British acquiescence in exchange for Spain's transfer of Florida to the British. Both antagonists gained something in the deal: The war ended, the British drove the French out of North America, and the French kept Louisiana out of Great Britain's hands.

Nearly four decades later, knowing that his overextended country lacked the ability to defend the vast and porous Louisiana Territory against incursion by aggressive and expansion-minded American settlers, King Carlos IV of Spain agreed to give the land back to France. In exchange, French dictator Napoleon Bonaparte gave Carlos the Grand Duchy of Tuscany, encompassing the cities of Florence, Pisa and Sienna.

The deal made Jefferson nervous; the United States had only recently concluded an undeclared naval war with France, and control of Louisiana meant control of the port of New Orleans and the ability to shut down traffic on the Mississippi River, a crucial trade and transportation route for Americans in the fertile Ohio River Valley. Jefferson's anxiety increased when he learned that Napoleon was preparing an invasion fleet bound for the Caribbean island of Santo Domingo, where Toussaint L'Ouverture had led an insurrection of black slaves that seized control of the French colony there.

From Santo Domingo, Jefferson realized, the imperialist French dictator could easily mount a naval invasion of the mainland, seizing New Orleans - through which more than a third of the United States' commerce passed - and pushing up the Mississippi as far as Canada. In effect, Napoleon might re-occupy France's old colonial empire in North America and force the young United States to meet any terms he wished to set. Napoleon did, in fact, plan just such an invasion, assembling a force of 10,000 men to occupy Louisiana.

Jefferson contemplated forming an alliance with Great Britain to fend off Napoleon, but he was spared this indignity. Napoleon's invasion force of 60,000 troops did reach Santo Domingo and overthrew L'Ouverture, but within a year 23,000 French soldiers had succumbed to a virulent epidemic of yellow fever - a viral infection spread by mosquitoes. Replacement troops were dispatched, but continuing sickness, insurrections and guerilla warfare brought the eventual French death toll to more than 50,000. The episode brought a halt to Napoleon's designs on North America; in 1803 he instructed his minister to sell the Louisiana Territory to the Americans, who had already been negotiating without much hope of success to buy the port of New Orleans.

The price settled upon was $11,250,000 for an estimated 820,000 square miles. The French government agreed also to pay $3,750,000 to settle damage claims from American citizens arising from the two-year naval war between France and the United States. The final price tag of $15 million works out to about 3 cents an acre. The transfer of ownership, formally concluded just before the Corps of Discovery left St. Louis to begin its 28-month journey, almost doubled the size of the United States.