Final answer:
Monroe was sent to Paris in 1803 to negotiate the purchase of New Orleans but ended up securing a deal for the entire Louisiana Territory, which became known as the Louisiana Purchase.
Step-by-step explanation:
In 1803, President Thomas Jefferson sent James Monroe to Paris to negotiate the purchase of New Orleans. However, due to the successful slave rebellion in Haiti and the resulting loss of French ambitions in the Americas, Napoleon Bonaparte decided to offer the entire Louisiana Territory to the United States. The purchase, known as the Louisiana Purchase, was an unprecedented real estate deal where the U.S. acquired approximately 828,000 square miles of land, substantially expanding the nation's size and agriculture potential for $15 million.