In 1803, U.S. President Thomas Jefferson created the Corps of Discovery and commissioned Meriwether Lewis and William Clark to lead an expedition into the American Northwest. Starting out in 1804, Lewis and Clark led an arduous expedition from the Mississippi River to the Pacific Ocean for a total journey of 3,700 miles on man-powered boats, horseback and foot. They faced many obstacles on their journey including bad weather, difficult terrain and dangerous encounters with some Native American tribes.

Geographical Obstacles

One of Jefferson’s goals with the expedition was to find a northwest water route to the Pacific Ocean. According to Al Bredenberg of the Smithsonian Museum of Natural History, Jefferson had expected that the Corps of Discovery would find a short and easy passage to the Pacific after leaving the Missouri. But instead the explorers had to endure a series of hardships, such as making their way along the Lolo Trail through the Bitterroot Mountains. The crossing of the Lolo Trail took 11 days and the travelers nearly starved. The expedition had to carry their boats in a process called portaging; they were only able to cover 4 to 5 miles a day. They would finally reach the Pacific coast in November 1805, a year and a half after setting out from St. Louis.

Bad Weather

Lewis and Clark's Expedition had to deal with thunderstorms, extreme heat and cold temperatures, hail storms and dust clouds. The team’s worst winter weather occurred at Fort Clatsop near the Pacific coast in early 1806. According to the U.S. Army Center of Military History, it rained all but 12 days that winter and the explorers’ clothes rotted off their backs.

Animals and Insects

The Corps of Discovery encountered many wild animals on their journey while making their way along the western rivers. Lewis was nearly killed by a grizzly bear in one recorded instance, and the team was confronted by no less than 40 bears on the expedition. Mosquitoes were also a major problem for the explorers. Sergeant John Ordway, the only member of the expedition who made a diary entry for each of the trek's days, wrote in his journal that the mosquitoes were “troublesome” and talked about how they caused swelling in his face and eyes.

Encounters with Native Americans

Although most encounters with Native American groups proved hospitable to the Corps of Discovery, the explorers did have one violent incident. When the group reached Travelers Rest in Montana, Lewis led a small team north up the Marias River. The group encountered some Blackfeet Indians and fought them. Although no members of the expedition were killed in the fighting, they killed two Blackfeet.