William Clark`s Map of the Lewis and Clark Trail
From the Rockies to the Pacific
On Google Maps.
Clark's map with overlays added by myself.
At the eastern edge of the top map there's a small loop in the trail, while in William Clark's map a straight line is drawn. On the trip westward, the expedition came out of the Rocky Mountains into a prairie filled with the Camas plant, whose root was a staple in the Nez Perce diet. They called the place "Quawmash Flats" after that plant, although it's now known as Weippe Prairie. The captains were in a hurry to get to the Pacific before winter, so they continued overland to the Middle Fork of the Clearwater River.
On the way back they had to set up camp and wait for the snow in the mountains to thaw, so they set up camp a few miles to the southwest of Weippe Praire, where they stayed until June 10, 1806. Captain Clark's map only seems to show one trace through that region, and that's what I highlighted.
At the point where the Clearwater River joins the Snake River from the west, there is another divergence in the Lewis and Clark Trail. On the westward journey they followed the Snake River down to its confluence with the Columbia River, while on the return trip eastward they took an overland shortcut back to the Clearwater.
On their way down the Columbia they came to a particularly difficult stretch of river extending some fifty-five miles through today's Columbia River Gorge. The natives would gather on the shore to watch as the expedition followed the falls in their canoes, portaging around only the most dangerous spots. The greatest falls were at the point where the Deschutes River joins the Columbia from the south. That site was known as the Celilo Falls, which no longer exist, as they were inundated when the Dalles Dam was constructed in 1957.
While still at Fort Mandan in early spring 1805, Meriwether Lewis wrote that he hoped to return to that spot before next winter. They didn't reach the Pacific Ocean until November, so they needed to wait out the winter of 1805-1806 by the mouth of the Columbia River. First they explored the north bank of the river, hoping to find a trading post or spot a merchant vessel at Cape Disappointment. They found neither traders nor a suitable place to set up winter camp, and were told by Clatsop Indians that there was a fitting location on the south bank of the Columbia. There they established Fort Clatsop, where they waited out the winter.