The historical significance of the Louisiana Purchase in 1803 lies in its vast territorial expansion of the United States, doubling the nation’s size and securing control over the Mississippi River. The purchase was negotiated by Thomas Jefferson, who aimed to ensure economic growth and access to trade routes. Acquired from France for $15 million, the Louisiana Territory spanned from the Gulf of Mexico to Canada, shaping westward expansion and manifest destiny. This acquisition not only provided fertile land for agriculture but also intensified debates over slavery and states’ rights, ultimately contributing to the sectional tensions that led to the American Civil War.