Lemhi Pass is where the expedition first crossed the Continental Divide. August 12, 1805. Lewis: at the distance of 4 miles further the road took us to the most distant fountain of the waters of the Mighty Missouri in surch of which we have spent so many toilsome days and wristless nights. thus far I had accomplished one of those great objects on which my mind has been unalterably fixed for many years, judge then of the pleasure I felt in all[a]ying my thirst with this pure and ice-cold water which issues from the base of a low mountain or hill of a gentle ascent for 1/2 a mile. Photo courtesy Ralph Maughan.

More from the journals about the Lemhi Mountains August 12, 1805. Lewis: the mountains are high on either hand leave this gap at the head of this rivulet through which the road passes. here I halted a few minutes and rested myself…. after refreshing ourselves we proceeded on to the top of the dividing ridge from which I discovered immence ranges of high mountains still to the West of us with their tops partially covered with snow. I now decended the mountain about 3/4 of a mile which I found much steeper than on the opposite side, to a handsome bold runing Creek of cold Clear water. here I first tasted the water of the great Columbia river. [Lewis is mistaken, this is not the Columbia, it's a headwater stream of the small Lemhi River.]

Find out more: Sierra Club in Idaho Rivers of Lewis and Clark Lewis and Clark in Idaho Kettle Range Conservation Group Sierra Magazine: Lewis and Clark