Spring 1806 had just arrived with the vernal equinox. Spring—the very word conjures images of warmth, comfort, family, friends, even to the most steadfast explorers. It is not surprising then that Lewis, Clark and many of the others, despite advice to the contrary, thought it was time for the expedition to start back to the "U. States." There were more justifiable reasons for starting back, however, were: food was in short supply, trade goods were nearly exhausted and the captains thought that a change in diet and location would help the many men who were sick. On March 23, 1806, the Lewis and Clark Expedition started back up the Columbia River—toward home.
It was mostly familiar ground, and the party kept up a good pace. By April 29, the expedition was camped on Walla Walla River just upstream from its mouth and about 10 miles south of present-day "Tri-Cities," Washington. Outfitted now with twenty-three horses, the party prepared for the overland journey from the Columbia to Lewis's (Snake) River.
Averaging a little less than twenty miles per day, the expedition, on May 4, reached the Snake River about 8 miles downstream from the mouth of Clearwater River. After a late breakfast near the river, the expedition then headed eastward up the Snake. At the present-day Idaho-Washington border the Snake River turns south; the party, however, continued along the Clearwater River.
On May 7, about 10 miles west of their 1805 Canoe Camp, the explorers left the river bottom and ascended the river hills to the south. Having reached the plateau, they headed east about 5 miles then turned south along the heights west of Clearwater River. After slogging all day, May 10, through several inches of fresh snow, the expedition descended a steep trail and, in the late afternoon, reached a Nez Perce village on Commearp (Lawyer) Creek less than 4 miles west of present-day Kamiah, Idaho. Here Big Arm, one of the Nez Perce chiefs, graciously invited the explorers to remain a few days as his guests.
Early in the afternoon of May 13, the expedition headed east down Commearp Creek to the Clearwater River. The party then continued north about a mile and made camp on the southwest side of the river. The next morning the men ferried equipment to the river's right bank then swam the horses across. The captains chose a site that provided a measure of defense. This would be their camp. Here they would wait while the sun melted the snow that blocked the Lolo Trail.
Shortly after establishing themselves at their new camp, the travelers built "tents" of sticks and grass to protect themselves from the elements. The Captains' shelter also made use of part of a sail. Though the shelter protected them to some degree from the night's cold, it failed to keep out the heavy rain that came down during the night of May 16-17.
On the morning of May 17, Lewis discovered that the chronometer had gotten thoroughly wet. He opened the chronometer's case, drained the water and attempted to dry the gears and springs with feathers. After cleaning out some rust, he put a few drops of bear's oil on the workings to lubricate them. He then wound and reset the chronometer. Unfortunately, he didn't specify at what time he reset it or how he derived that time.
The expedition remained twenty-seven days at this camp, but the captains—contrary to their usual custom—never gave it a name. Elliott Coues, in his edition of the expedition's history (1893), called it Camp Chopunnish, a name which it appropriately retains.