After the Louisiana Purchase doubled the size of the United States, it was vital that this vast wilderness-- considered uninhabitable by many--be explored and mapped. The two brave adventurers chosen to lead this Corps of Discovery were Meriwether Lewis and William Clark. The incredible story of their adventurous and treacherous exploration of the United States' western frontier is an action-packed narrative told through contemporary primary sources. Interest Level: 5-8 Reading Level: 6.7 ATOS Book Level: 8.4 AR Interest Level: MG AR Points: 2 AR Quiz: 73061EN.