Meriwether Lewis and William Clark led the first U. S. expedition across the continent. In 1804 a hopeful Thomas Jefferson sent Captains Meriwether Lewis and William Clark to find the fabled River of the West. From the time of Columbus, explorers and statesmen had dreamed of a Northwest Passage, an all-water route connecting the trade routes of the Pacific to the Old World of the Atlantic. As president of a still-young nation, Jefferson had pressed for the Louisiana Purchase to strengthen American trade and settlement. The final $15 million-dollar agreement with France doubled America's size overnight. President Thomas Jefferson sent them to find the headwaters of the Missouri River and a river to the Pacific Ocean.

Throughout the expedition, Lewis and Clark gathered crucial information about this new territory and carefully recorded all of their findings in journals. About one quarter of their expedition was in what is now Montana. The following are some of the major discovery points in this journey though Montana:

1. Fort Union
2. Glasgow and the Milk River
3. Fort Peck
4. Charles M. Russell National Wildlife Refuge
5. Missouri Breaks
6. Fort Benton
7. Loma and Marias River
8. Upper Missouri
9. Great Falls
10. Gates of the Mountains
11. Helena
12. Missouri Headwaters
13. Beaverhead Rock
14. Clark's Lookout
15. Camp Fortunate
16. Lost Trail
17. Ross' Hole
18. Travelers Rest
19. Lolo Hot Springs
20. Lolo Pass
21. Pompeys Pillar
22. The Yellowstone River
23. Camp Disappointment