From the head of the falls they took a fresh start, with an additional canoe that was built there. Throughout this locality they heard the strange booming sounds which are a feature of the region and have not been explained. It was not long before they were confronted by three forks of almost equal dimensions, and they were puzzled as to which was the proper one to choose, the easiest to arrive at the head of some Pacific slope river. While considering the matter they bestowed the names of Jefferson, Madison, and Gallatin upon them in the order named from west to east. At last they concluded to ascend the Jefferson, and in this they made no mistake. They pushed up towards its source, following Beaverhead branch, Horse Prairie Creek, and Trail Creek, and on August 12, 1805, Captain Lewis, who had gone somewhat in advance, came, in Lemhi Pass, to the final rill of the Missouri and soon stood beside another brook that swept westward to swell the flood of the Columbia, the first white man to surmount the Backbone of the Continent between Peace River, far to the north, and New Mexico, far to the south. He looked out upon an absolutely unknown portion of the Wilderness,—an area many times that of Spain, which still claimed it. Escalante had been from Santa Fé to Salt Lake valley, but west and north of his route, to the head of Fraser River, no white man had ever penetrated. [Illustration: The Dalles of the Columbia. Photograph by F. S. Dellenbaugh.] Still advancing before the main body, he met with some stragglers from and then a band of Shoshones, some of whom he had been anxious to meet for the purpose of securing information, for while we speak of the country as unknown, it was, as before noted, only so to white men. The natives knew it perfectly. From these people he borrowed horses and prevailed on the chief to return to the main party with him, a proceeding the chief was doubtful about, for never before having seen white men (though the Lewis and Clark party were so tanned they might have passed for natives) he was fearful of some treachery. On meeting the party, the chief discovered that Sacajawea was his sister, who in childhood had been stolen by the Minitarees. The whole band were overjoyed at seeing this woman whom they had never expected to meet again. Proceeding to the camp of these people, a halt was made while Captain Clark explored in advance down this Lemhi branch and Salmon River into which it flowed. The Shoshones had told them that the country below in this direction was too rough to travel far in any manner, and Clark found out the exactness of this information and returned. With guides from the Shoshone band they then proceeded down the Lemhi branch and over to North Fork which they mounted, thence cutting their way across the range and descending to Ross's Hole on the head of Bitter Root River. This stream they followed down to the mouth of Lolo Creek, where they made a camp called Traveller's Rest.