For almost three decades, the best storehouse of scientific knowledge about the vast new American territory in the west existed in one room — the office of William Clark in St. Louis. After the return of the Corps, President Jefferson expected Lewis to turn their raw notes and maps into a finished, "scientific" account that could be used by other explorers, immigrants or settlers. Lewis made little progress before his death in 1809, so the job and the journals fell to Clark. Over the next few years, Clark was named Governor of the Missouri Territory and was a partner in the Missouri Fur Company.
Clark’s map was important. Hundreds of fur traders employed by Clark’s company would refer to his map before they set out. And as new expeditions were mounted to explore other regions in the West, the explorers would stop and learn from Clark’s map.
In turn, when they came back east, traders, trappers, explorers and even Native Americans would bring Clark new information. He would use that information to update his master map of the West. In 1814, a publisher in Philadelphia issued a two-volume journal entitled:
History of the Expedition under the Command of
Captains Lewis and Clark.
It included an engraved version of Clark’s map and became a standard reference for travelers in years to come.
Other explorers like Pike, Long, and Fremont greatly enhanced the geographic knowledge about the West. They made it possible for later immigrants to follow.