7What was the Louisiana Purchase and why was it important? How did the Louisiana Purchase change the United States? How did it affect the future for black people and American Indians? When the United States bought the Louisiana Territory from France in 1803, it would lead to historic changes for the young country. Using an inquiry-based approach, primary sources, and quick-reference infographics, readers will learn the history behind the Louisiana Purchase and how it affected the future of America and its people.