Among Lewis and Clark's many objectives on their expedition into the Louisiana Purchase were claiming territory and making accurate maps. Thomas Jefferson instructed Meriwether Lewis on June 20, 1803, to take observations of latitude and longitude at remarkable points on the river, especially at the mouths of rivers, rapids, islands, and other places marked by durable natural features that could be recognized later. On April 21, 1805, Capt. Lewis reached the upper point of the timbered bottom on the larboard side below a high bluff point they called Cut Bluff, and at 1 mile passed White Earth River on the starboard side. On April 22, 1805, he ascended to the top of Cut Bluff, where he viewed a countryside that, except for the valley formed by the Missouri, was without timber or underbrush and revealed immense herds of buffalo, elk, deer, and antelopes feeding in a common and boundless pasture.