How were the Chinook discovered?

The Chinook were first noticed generally by Lewis and Clark in 1805, and afterwards were greatly diminished in numbers by diseases brought by white trades. The Lewis and Clark Expedition (1804-1806) was the first overland expedition undertaken by the United States to the Pacific coast and back. The expedition team was headed by Meriwether Lewis and William Clark and assisted by Sacajawea and Toussaint Charbonneau. The expedition's goal was to gain an accurate sense of the resources being exchanged in the Louisiana Purchase. The expedition laid much of the groundwork for the Westward Expansion of the United States.