Final answer:
The exact phrase used by Lewis and Clark when they sighted the Pacific Ocean is not historically recorded, but the event marked the culmination of their rigorous journey across the North American continent that lasted from 1804 to 1806.
Step-by-step explanation:
The student is asking about the historic phrase exclaimed by the Corps of Discovery, led by Meriwether Lewis and William Clark, when they saw the Pacific Ocean for the first time during their expedition. This phrase signified a momentous occasion as they had traversed the continent in search of the Pacific and a potential Northwest Passage. After a long and grueling journey, which included near-starvation in the Bitterroot Mountains and establishing relationships with numerous Native American tribes, they reached their goal, although the exact phrase is not recorded in history. The significance of the moment was profound, not because of a recorded phrase, but because they had arrived at a vast and previously uncharted territory from which they would collect valuable information and map the area, albeit their primary mission to find an all-water route was not achieved, as it did not exist.