Final answer:
The return trip east to St. Louis for the Lewis and Clark expedition took approximately six months, concluding their journey that started in May 1804. They had spent the winter of 1805-1806 in Oregon, and after the hardships faced during nearly two years of travel, they returned to St. Louis in September 1806.
Step-by-step explanation:
The Lewis and Clark expedition, an iconic journey tasked with exploring the newly acquired Louisiana Territory and helmed by Meriwether Lewis and William Clark, took nearly two years to reach the Pacific Ocean.
After setting out in May 1804, they faced numerous hardships including fierce weather conditions, interactions with wildlife, and navigating relationships with Native American tribes.
Given the goal to discover commercial possibilities, map the territory, and establish United States claims to the land, the explorers spent the winter of 1805-1806 in Oregon.
During the return trip east to St. Louis, the Corps of Discovery, as the group came to be known, took a shorter duration to traverse back across the continent.
The expedition returned to St. Louis later in 1806, after setting forth from their winter camp when the season allowed. This return journey was faster than the outward leg, as the team took approximately six months to complete the eastward trek, arriving back in September 1806.
Their achievements greatly contributed to the nation’s knowledge of what lay west of the Mississippi, although they did not find the hoped-for Northwest Passage. Nevertheless, their exploration played a crucial part in the expansion of the United States and provided a wealth of information on the geography, flora, and fauna of the vast western lands.