The Lewis and Clark expedition was very influential. The journals kept by the explorers were read and used as guidebooks by the early mountain men; these explorers would ultimately help set the trails for the early Oregon Trail in the 1840s. Lewis and Clark established an American claim to the Oregon Territory which would become a later diplomatic bone of contention between Britain and the United States. The expedition also established that there was no Northwest Passage; this was the fabled waterway that would connect the Atlantic Ocean to the Pacific via a river through the American continent, thus making European-Asian trade easier. Lewis and Clark's voyage was a diplomatic and military voyage first and foremost--the explorers made contact with many native American tribes. This was the U.S. government's first contact with the Sioux nation of the High Plains--this tribe told the explorers to keep traveling on. The Sioux were recently decimated by a smallpox outbreak and were not trustful of the new explorers. Lewis and Clark brought back many animal and plant specimens specifically for Thomas Jefferson, and many of the bones brought back fueled an early American interest in paleontology.