"Among all the facets of his [Thomas Jefferson's] scientific inquisitiveness nothing had so captured his imagination as the mystery shrouding the geography of interior North America. This was not a recent interest. His boyhood guardian had been Dr. Thomas Walker, the first explorer of Kentucky, and that great frontiersman's stories had stirred in him a desire to know more about the west which had never flagged and had never been satisfied."
A view of the Cumberland Gap, an area of Kentucky explored by Dr. Thomas Walker.
The route of Dr. Thomas Walker, the explorer, through the Cumberland Gap can be seen here.
There was also a history between my ancestor, Christopher Acklin, and Dr. Walker (as well as Walker's son, Francis).
Since President Jefferson commissioned the expedition, a case could be made that the Lewis and Clark Expedition had its roots in the explorations of Dr. Thomas Walker.