WASHINGTON -- Satellites are taking sharp-eyed snapshots of a trail traveled nearly 200 years ago that opened up vast expanses of the unexplored American frontier to the fledging United States.

The heroic expedition led by Meriwether Lewis and William Clark from 1804-1806 took the team across approximately miles 3,700 (6,000 kilometers) of uncharted wilderness. Now, satellite imagery is mapping their pathway to help reveal the contrasting ecological, environmental and cultural changes that have occurred over the past two centuries.

A NASA-funded Earth Observing System Education Project is underway at the University of Montana in Missoula. The campus is the site of a National Lewis and Clark Education Center (NLCEC). At the heart of the enterprise is the latest in remote sensing gear, coupled with interactive and multi-media software, along with high-tech computing hardware.

Numbers of spacecraft have already focused in on segments of the Lewis and Clark Trail, said Alex Philp, director of the NLCEC. NASA's Terra and Landsat 7 satellites have clicked views, as has Space Imaging's IKONOS, and an Indian Remote Sensing satellite, he said.

Using the satellite photos, coupled with overlays of geographical and multimedia information, animated fly-throughs for portions of the Lewis and Clark Trail have already been assembled, Philp said. "Lewis and Clark becomes a theme. It's a way to introduce technology to teachers. It gets them using satellite remote sensing before they even know they are doing it, because they are interested in the trail, while we are focusing on the concept of 200 years of change," he told SPACE.com.

In a very real sense, the Lewis and Clark sojourn can be seen as an early 19^th century version of "space" travel - an arduous and pioneering plunge into terra incognita.

Shortly after his election in 1801, U.S. President Thomas Jefferson began to plot an expedition to trace the boundaries of the Louisiana Territory -- newly purchased from France -- and lay U.S. claims to the Oregon region.

The President's plan also called for recording scientific data about the regions and establishing contact with the indigenous people who lived in those regions, noting their languages and culture.

Jefferson believed that a route to the Pacific coast along the Missouri and Columbia rivers could be part of a land-and-water passage between the Atlantic and Pacific oceans. Trade routes and commerce were envisioned.

In January 1803, in a confidential letter to Congress, Jefferson requested funds to bankroll an expedition to the Pacific.