“[President Jefferson] knew that future mapmakers, naturalists, and other scientists would rely on the valuable first-hand knowledge that Lewis and Clark collected. He encouraged them to make their observations ‘with great pains and accuracy … for others as well as yourself.’ That meant that every time they encountered an unfamiliar plant, animal, landscape feature, or cultural item – the Louisiana Territory and the western portion of the continent teemed with them – they had to invent a new term.”