Answer:
Against this military background, in May 1804, Meriwether Lewis, now Jefferson’s private secretary and previously a captain in the 1st Infantry, and William Clark, now a second lieutenant in the artillery, set out with an army expedition to assert American claims to Louisiana and, if possible, to march to the Pacific Ocean, which Jefferson hoped would one day see the American flag. Jefferson’s instructions dealt mainly with the geography and the Indians Lewis and Clark would meet on the way–a primary objective was ‘to explore… the most direct and practicable water communication across the continent, for the purpose of commerce.’ But Jefferson also hoped to assert the United States’ ownership of Louisiana, by use of military force if necessary.