"This morning we set out at 7 A.M. steered North 25 (degrees) East 12 Ms. to Kimooenim Creek (Tucannon) through a high level plain. This creek is about 12 yards side, pebbly bottom, low banks and discharges a considerable body of water. It heads in the S.W. mountains and discharges itself into Lewis River (Snake), a few miles above the narrows. The bottoms of this creek are narrow, with some timber principally cottonwood and willow., the underbrush such as is mentioned on N.E. creek. The hills are high and abrupt. The land of the plains is much more fertile than below, less sand and covered with taller grass; very little of the aromatic shrubs (sage) appear in this part of the plain. We halted and dined on this creek after which we then proceeded North 45 (degrees) E. three miles through high plain, (about the summit of this plain the party entered Garfield County) to a small creek (Pataha) 5 yards wide branch of the Kimooenim Creek, this stream falls into the creek some miles below. The hills of this creek like those of the Kimooenim are high, its bottoms narrow, and possesses but little timber; lands of good quality a dark rich loam. We continued our route up this creek on the N. side, 75 (degrees) E. 7ms. the timber increases in quantity, the hills continue high. East 4 miles up the creek.  Here we met We-ark-koomt whom we have usually distinguished by the name of the Big-Horn chief from the circumstance of his always wearing a horn of that animal, suspended by a cord to the left arm. He is the first chief of a large band of the Choppunish nation (Nez Perces). He had ten of his young men with him. This man went down Lewis (Snake) River by land as we descended it by water last fall quite to the Columbia and I believe was very instrumental in procuring us a hospitable and friendly reception among the natives. He had now come a considerable long distance to meet us. After meeting this chief we continued still up the creek bottoms N. 75 (degrees) E. 2ms. to the place at which the road leaves the creek and ascends the hills to the plain. Here we encamped in a small grove of cottonwood trees which in some measure broke the violence of the wind. We came 28 Ms. today. It rained, hailed, snowed and blowed with great violence the greater portion of the day. It was fortunate for us that this storm was from the S.W. and of course on our backs. The air was very cold. We divided the last of our dried meat at dinner when it was consumed as well as the balance of our dogs, nearly. We made but a scant supper and had not anything for tomorrow; however We-ark-koompt consoled us with the information that there was an Indian lodge on the river at no great distance where we might supply ourselves with provisions tomorrow. Our guide and the three young Wallawollahs left us this morning rather abruptly and we have seen nothing of them since. The S.W. Mountains appear to become lower as they proceed to the N.E. This creek reaches the mountains.  We are nearer to them than we were last evening."

     Captain Clark's diary for May 3, 1806, is almost identical with that of Captain Lewis.  In fact it was Clark's custom to copy Captain Lewis' notes when they were together.  Lewis was better educated and a better writer.  Clark made several side excursions during the course of the expedition and on such occasions was of course compelled to write his own accounts, which were sometimes poorly written and contained mistakes in grammar and spelling.  His entries however were accurate and to the point. The following is a quote from Captain Lewis' diary of Sunday, May 4, 1806.

     The Nez Perce Trail which the party was following struck Stember Creek near the Stember Creek Bridge on the present highway between Pomeroy and Lewiston.  The earliest vehicle road followed the course of the trail.  Scars of the old road and trail and of numerous parallel travois tracks can still be seen on the ridge immediately west of the bridge, leading from the Alpowa Flat down to the Stember Creek bottom.
At that time of the year Stember would carry considerable water and Lewis naturally referred to it as the source of the Alpowa Creek which he followed to the Snake River.