How did a shipwreck double the size of the United States?

The Founding of New Orleans

A street sign in New Orleans reflects its period under Spanish authority.
A street sign in New Orleans reflects its period under Spanish authority.

King Carlos II of Spain was cousin to King Louis XV of France through the Bourbon bloodline. In 1762, Louis ceded the Louisiana Territory to Carlos with the Treaty of Fontainebleau. The land grant wasn't motivated by fond familial regard; Louis sought keep his precious Louisiana Territory out of British hands. The French had lost the Seven Years' War to the British, and King Louis foresaw the upcoming repercussions. The next year, Britain and France signed the Treaty of Paris that ended the war officially and gave the English all of Louisiana east of the Mississippi River -- except for New Orleans.

In 1682, explorer Robert Cavelier de La Salle discovered the mouth of the Mississippi near present-day New Orleans and named the land "Louisiana" in honor of King Louis XIV. De La Salle failed to establish a lasting settlement, but Pierre LeMoyne Sieur d'Iberville arrived 17 years later and started Fort Maurepas about 70 miles (112 kilometers) northeast of New Orleans. Hearing the news, King Louis XV granted permission to start a French colony, and New Orleans became the capital city in 1718.

New Orleans' geography had its share of pros and cons. Hordes of mosquitoes attracted to the waterlogged city's climate bred disease, including yellow fever and smallpox. Yet New Orleans was prime commercial real estate. Farmers and traders could send their goods down the Mississippi River to the Gulf of Mexico via New Orleans, then ship it anywhere in the world. Spain exploited its control over the port and levied expensive tariffs for its use. But those export profits didn't insulate New Orleans or the Spanish government from the loss of money that sank with El Cazador. As more people settled in the sprawling Territory, it became even more unwieldy -- and costly -- for Spain to manage.

Around that time, France started eyeing its former territory again. Napoleon took the French throne by coup in 1799, and he looked to the West to expand his empire. On Oct. 1, 1800, Spain and France signed the secret Treaty of San Ildefonso. With it, Napoleon cut a deal to give the King of Spain's son-in-law the Tuscan throne in exchange for returning the Louisiana Territory to French control. At the same time, trouble was brewing in French-owned Hispaniola that would indirectly alter the United States' fortune forever.