The Louisiana Territory was a vast area of land in North America that was purchased from France in 1803. This acquisition, known as the Louisiana Purchase, doubled the size of the United States and included land that would eventually become several states, including Louisiana, Arkansas, Missouri, Iowa, North Dakota, South Dakota, Nebraska, and parts of Montana, Wyoming, Colorado, and Kansas. The territory was explored by Meriwether Lewis and William Clark from 1804 to 1806, a journey known as the Lewis and Clark Expedition. Their exploration provided valuable information about the geography, resources, and native peoples of the region, paving the way for westward expansion in the United States.