Answer;
Long time no sea
Step-by-step explanation;
The route of Lewis and Clark's expedition took them up the Missouri River to its headwaters, then on to the Pacific Ocean via the Columbia River, and it may have been influenced by the purported transcontinental journey of Moncacht-Apé by the same route about a century before.
Their mission was to explore the unknown territory, establish trade with the Natives and affirm the sovereignty of the United States in the region. One of their goals was to find a waterway from the US to the Pacific Ocean.