Two centuries ago, on May 14, 1804, American explorers Meriwether Lewis and William Clark led an expedition to explore the western part of the American continent and hopefully find a river route to the Pacific Ocean. It was a journey that would change America forever. The journey helped open the American West and eventually bound the nation from the Atlantic to the Pacific. There are still parts of the route that are open and free just as they were in 1804, but there are other portions that have been completely transformed.

The United States was new, but already it was looking westward. In 1804 President Thomas Jefferson, a man of great invention and curiosity, commissioned an expedition to explore the great unknown of the western expanse. He did this for mostly practical reasons, historian Ronald Grim says.

?The Lewis and Clark expedition was sent out by Thomas Jefferson to explore the northern part of the Louisiana Purchase, because Jefferson had major designs on expanding the U.S. across the whole continent,? he explains.

In one of history?s greatest land deals, the Louisiana Purchase, France sold the U.S. the western territories that extended from the Mississippi river to the Rocky Mountains.

The object of the expedition was to find a water route from the eastern U.S. to the Pacific Ocean, in order to open trade.

?It was an adventure into the unknown,? explains Mr. Grim. ?And this has to be similar to the feeling our astronauts would have had.?

Jefferson chose his personal secretary, Merriweather Lewis, to head what was called the Corps of Discovery.

Lewis then chose Captain William Clark, an experienced frontiersman.

?It was a good match in Lewis and Clark,? says Mr. Grim. ?Clark seems to be the more practical; he was the one doing the actual surveying and mapping. Lewis seems to be more the idealist, the more spiritual of the two.?

In a keelboat like this, the party of several dozen men set out from St. Louis, traveling upriver against the current. One of their primary objectives was to make contact with native Indian tribes along the way. Lewis and Clark knew that their success depended on safe passage from these native peoples.

In the winter of 1804 the Corps of Discovery built a fortress by the Mandan Indian village, near what is today Bismarck, North Dakota. Tim McLaughlin is a historian and guide at Fort Mandan. He says that the Corps of Discovery depended on the Indians, and in turn traded goods.

?This was very popular and the blacksmiths made many of these that they traded for corn and squash and sunflower and such,? says Tim McLaughlin.

It was during this winter at Fort Mandan that a young Indian woman joined the Corps of Discovery. Sacagawea was an unlikely ally who would save the future of the expedition on more than one occasion, according to museum director David Borlaug.

?A young Indian woman, carrying a baby, when tribes from Montana out west, who had never encountered white people before,? he notes. ?They saw all these men, these boats, these guns, then they saw a young woman with a baby. That did convince them that this is what Thomas Jefferson wanted this to be, a party of peace and friendship.?

Lewis and Clark had expected mountains to divide the continent with maybe a short land passage to another river flowing west to the Pacific Ocean.

?But imagine their surprise when they got to the front range of the Rocky Mountains,? says historian Ronald Grim. ?They climb up that first range of mountains. They thought there was a single range. But at that point they saw nothing but more mountains and more mountains.?

The winter of 1805 nearly broke the expedition. By land and in snow, they traversed the Bitterroot Mountains until finally finding the west-flowing Columbia River that would take them to the Pacific Ocean.

?They finally made it to the Pacific ocean,? he explains. ?As William Clark wrote in his journal, ?ocean in view, oh the joy'.?

Lewis and Clark did not find the water passage to the west they had hoped for. But they made scientific observations of the plants and wildlife they found.

They also established friendly relations with native Indian tribes that, unfortunately, would not last.

?The real manifestations of westward expansion didn?t truly reveal themselves for a few decades, but it did all start with Lewis and Clark,? says David Borlaug.

?This was the event that opened up the American interest in the west,? adds Ronald Grim. ?This was the beginning of Americans thinking about extending their country from the east coast to the west coast.?