David Oscarson William Clark Sapphire PenIn May, 1804, Meriwether Lewis and William Clark set out on an expedition of epic proportion. Having accepted the charge from President Thomas Jefferson, their mission was to explore, map and document the vast new region of the United States acquired through the Louisiana Purchase. This fearless ensemble, known as The Corps of Discovery included Sacagawea, her son, Pompey, 45 young frontiersmen and Seaman (Captain Lewiss 150 pound Newfoundland dog).