When did American explorers come to the northwest?

American explorers began venturing into the Northwest region of the United States in the late 18th and early 19th centuries. Notably, the Lewis and Clark Expedition, commissioned by President Thomas Jefferson, explored the area from 1804 to 1806, mapping the territory and establishing American claims. Other explorers, such as fur traders and settlers, followed in subsequent years, drawn by the region's resources and potential for expansion.