Where did most of the american people live prior to the louisiana purchase?

LOUISIANA PURCHASE. A watershed event in American history, the purchase of the Louisiana Territory from France in 1803 nearly doubled the land mass of the young nation: for a purchase price of $15 million, the United States increased its size by some 828,000 square miles. The region included the Mississippi River and its tributaries westward to the Rocky Mountains, and extended from the Gulf of Mexico at New Orleans up the Red River to the Canadian border.