On November 18, 1805, Captain William Clark of the United States Army and eleven men, including Clark’s slave York, explored the mouth of the Columbia River and beheld the Pacific Ocean for the first time. Clark, along with Captain Meriwether Lewis, had led an exploratory expedition from St. Louis to the Pacific, which had set out in May of 1804. They were the first citizens of the United States to make an overland journey to the Pacific. Clark noted that the “men appear much Satisfied with their trip beholding with estonishment the high waves dashing against the rocks & this emence Ocian.” Clark carved his name on a tree overlooking the ocean with the wonderfully understated caption, “By Land from the U. States in 1804 & 1805.”1 The Lewis and Clark expedition was one of the remarkable achievements of Thomas Jefferson’s two-term presidency. The expedition was the apotheosis of the ideological vision of the third president, who conceived of the expedition as a commercial, scientific, and diplomatic exercise. As such, it was the capstone of Jefferson’s vision of an expansive American republic.