<P> According to Thomas Jefferson himself , one goal was to find `` the most direct and practicable water communication across this continent , for the purposes of commerce . '' Jefferson also placed special importance on declaring U.S. sovereignty over the land occupied by the many different tribes of Native Americans along the Missouri River , and getting an accurate sense of the resources in the recently completed Louisiana Purchase . The expedition made notable contributions to science , but scientific research was not the main goal of the mission . </P>
on which river did the exploration of the louisiana purchase begin
Missouri River