* In 1801, Thomas Jefferson became president of the United States. One of his goals was to explore the vast western territories that had been acquired by the Louisiana Purchase.
* Jefferson appointed Meriwether Lewis, his personal secretary, and William Clark, a skilled woodsman and explorer, to lead the expedition.
* Lewis and Clark assembled a team of about 30 men, including soldiers, frontiersmen, and scientists.
* The expedition set out from St. Louis, Missouri, in May 1804.
* The explorers traveled up the Missouri River, across the Rocky Mountains, and down the Columbia River to the Pacific Ocean.
* Along the way, they encountered a variety of Native American tribes and learned about their cultures and customs.
* Lewis and Clark also made detailed observations of the plants and animals they encountered.
* The expedition returned to St. Louis in September 1806.
* Lewis and Clark published a detailed account of their journey, which became a bestseller.
* The expedition provided a wealth of information about the western United States and helped to open up the region to further exploration and settlement.