The Unknown

• Jefferson hoped the expedition would find a water route that linked the Columbia and Missouri rivers. Such a route would connect the Pacific Ocean to the Mississippi river system, and open trading ports of the east to the west. At the time, however, American and European explorers had only visited portions of what would become the beginning and end of the route Lewis and Clark would travel. No one knew what laid in between. Jefferson believed woolly mammoths, erupting volcanoes and mountains of salt awaited the expedition, according to an article from National Geographic. With no way of knowing what to expect, preparing for the expedition became the first obstacles Lewis and Clark had to overcome.
  
  

Indians

• Uneasy relations between settlers and Indian tribes along the frontier meant the expedition would travel through territory controlled by potentially hostile forces. Lewis and Clark prepared for these encounters by bringing with them peace medals bearing the image of Jefferson on one side and two hands shaking on the other. When encountering a tribe, the captains would explain the land now belonged to the U.S., and that man in the east, Jefferson, was the tribe's new "great father," according to an article from PBS. Not all tribes accepted the expeditions tribute, and an encounter with the Teton Sioux nearly resulted in a battle. The expedition made camp on river islands whenever possible, and always posted guards to warn against Indian raids during the night.
  
  

Geography

• The geography of the unexplored terrain was difficult to navigate. Mountains, waterfalls and rivers all presented different challenges for the expedition to overcome. An exhausting and difficult ordeal, traveling upstream on the Missouri required oars and long poles to push the boats against the current. Occasionally the boats had to be pulled upriver with ropes by men walking along the shore, according to the National Parks Service. It took the expedition more than a month just to navigate down the Great Falls of the Missouri River. Crossing the Rocky Mountains required the corps to acquire horses from the Shoshone tribe, who used their bargaining position to extort a high price for horses in poor physical condition, according to National Geographic.
  
  

Weather

• Harsh winters would freeze the Missouri rivers solid, so the corps had little choice but to make camp when winter hit. The corps made its first camp among the Mandan tribe in modern day North Dakota. The corps quickly built a fort to protect themselves from the harsh cold and potential attacks from the nearby Teton Sioux. Limited supplies forces the expedition to hunt buffalo and elk in order to survive the winter. Winter in the Pacific was less harsh, but the constant rain and an inability to contact the East left corp members depressed and weary.