Meriwether Lewis was an American explorer best known for his role in the Lewis and Clark Expedition, a mission to explore the newly acquired Louisiana Territory. He was born in Virginia in 1774 and served in the United States Army before being appointed by President Thomas Jefferson to lead the expedition. His co-leader was William Clark, and together they explored the Missouri River and the Pacific Northwest. Lewis was also a scientist and cartographer, and his work helped to open up the West to further exploration and settlement.