After trekking over four thousand miles, Meriwether Lewis, William Clark, and the Corps of Discovery sighted the Pacific Ocean. The two great explorers carved their names on trees to prove that U.S. military officers had reached the Pacific by land. Lewis and Clark failed to achieve their ultimate goal of finding a direct water route across the continent. However, the explorers discovered numerous animal and plant species unknown to western science, mapped uncharted territory, interacted with many American Indian nations, and helped open up the West for American expansion.