On May 14, 1804, explorers Meriwether Lewis and William Clark embarked on a heroic expedition; their mission was to travel from the mouth of the Missouri River, near St. Louis, to the Pacific Ocean - and back again. Lewis and Clark led the expedition, known as the Corps of Discovery, on an 8,000-mile journey. For 28 months they explored much of the territory of Louisiana while mapping rivers, collecting plants and animals new to science, holding councils with Native Americans, and keeping detailed journals.

Close Up: For this stamp, artist Michael Deas envisioned a landscape evoking the spirit of the Corps of Discovery. The scene needed to be accurate in every detail, from the men's clothing and accoutrements, to the topography of the specific vista they are surveying. Diaries were consulted to determine where the two explorers would have been together – they were apart more often than you would expect. The artist was even lent accurate reproductions of the explorers' clothing, for his models to wear.