Final answer:
Lewis and Clark's expedition expanded the United States westward to the Pacific Ocean, mapping the newly acquired lands and strengthening American territorial claims.
Step-by-step explanation:
The lands acquired by the United States that were explored by Lewis and Clark in their expedition expanded the nation westward until it reached the Pacific Ocean. Despite initially setting out to find a water route across the continent, which they did not find as there is no all-water Northwest Passage, Lewis and Clark were successful in adding to the knowledge of the lands west of the Mississippi River. Their voyage directly contributed to the solidification of the United States' claim to the immense territory, and they documented and mapped much of the region, paving the way for future American territorial expansion and trade.