What if Lewis and Clark had not returned?

In 1803,
President Thomas Jefferson sent his personal secretary,
Meriwether Lewis, on what may have been the American government’s first
fact-finding junket. They were “to map the land, hold diplomatic councils with
native peoples, and study and record everything regarding plants, animals,
minerals, soil, and native ways of life" in the vast and largely unknown Louisiana
Purchase which had only recently been purchased by the United States.
Lewis dutifully organized an expedition composed of his former commander,
William Clark, and approximately 45 men and
headed into the wilderness to fulfill his mission. Two years and four months
later, long after they had been given up for dead, they returned. The expedition
“logged more than 8,000 miles...interacted with dozens of native
tribes...mapped a broad swath of the Rockies and the courses of the Missouri and
Columbia...[and] wrote the first scientific descriptions of a breathtaking 178
plants and 122 animals”
but alas, did not find the much-sought-after northwest passage to the
Pacific. Although they had several dicey encounters with the inhabitants which
could easily have escalated, the Corps escaped relatively unscathed, losing only
one man to disease.
Their so-called Voyage of Discovery has been an inspiration to American
school children, a source of pride, and a guide for westering pioneers for the
intervening two centuries.
What if they never came back?