MAP 8.1 Lewis and Clark and Zebulon Pike Expeditions, 1804–1807 The expeditions led by Meriwether Lewis, William Clark, and Zebulon Pike illustrate the vast regions explored in just four years after the purchase of the Louisiana Territory by the United States. Lewis and Clark as well as Pike journeyed through and beyond the borders of that territory, gathering important information about Indian nations, plants, animals, and the natural terrain throughout the West.