On July 16, 1805, as the Expedition was about to enter the Rocky Mountains, Lewis described rapids immediately at the foot of the mountain where the Missouri first enters and wrote of a large pine tree on a small island at the head of those rapids, the first mention of Pine Island. Later, at winter camp on the Pacific Coast while compiling lists of rivers, creeks, and significant geographical places, Clark included Pine Island with mileage distances to other locations. Clark again used Pine Island as a geographical reference point when describing Lewis' route over the Rocky Mountains and along the Road to the buffalo in July of 1806.