Thomas Jefferson was the third president of the United States, serving from 1801 to 1809. During his presidency, he expanded the United States in a number of ways.
* Louisiana Purchase: In 1803, Jefferson negotiated the Louisiana Purchase with France. This agreement doubled the size of the United States, adding 828,000 square miles of land.
* Lewis and Clark Expedition: Jefferson also sent the Lewis and Clark Expedition to explore the newly acquired Louisiana Territory. This expedition lasted from 1804 to 1806 and was led by Meriwether Lewis and William Clark.
* Zebulon Pike Expedition: Jefferson also sent Zebulon Pike to explore the western United States. Pike's expedition lasted from 1806 to 1807 and explored the areas that are now Colorado, Kansas, Nebraska, and Oklahoma.
* Acquisition of Florida: In 1819, Jefferson negotiated the acquisition of Florida from Spain. This agreement added another 70,000 square miles of land to the United States.
Jefferson's expansion of the United States had a number of important consequences. It increased the size of the country, doubled its population, and added a number of new states. It also helped to improve relations with France and Spain, and to establish the United States as a major power in the world.