" Capt. Lewis is brave, prudent, habituated to the woods, and familiar with Indian manners and character,” Jefferson told Benjamin Rush.95 Lewis asked William Clark, George Rogers Clark’s brother, to join him in organizing what became known as the Corps of Volunteers for North West Discovery.96 Jefferson thought of America as an “empire of liberty.” Now he would have a keener, more detailed grasp of the continent that stretched far beyond the nation’s existing borders—and a chance at claiming that sprawling West. "

― Jon Meacham , Thomas Jefferson: The Art of Power