Lewis and Clark prepared these documents at Fort Clatsop and later, as rough equivalents of the "Estimate of the Eastern Indians" which was drawn up at Fort Mandan. However, the material here provides much less information than the earlier document, being largely confined to names, locations, and estimated numbers. The "Western Indians" are those located west of the Continental Divide, especially on the Columbia drainage and the Northwest Coast. Much of the information would have come from Indian informants, since it chiefly concerns tribes wholly unknown to whites, except for those on the coast and those met by the party on their route of travel. Some of these tribes the captains had never actually seen, and among those they had seen were many obscure bands, subdivisions of larger groups now long extinct or absorbed into others. Identification in a number of cases is problematical.
The first item is in both Lewis's and Clark's hands and is found in Codex I. Lewis's part covers the Indian tribes the party encountered from the Rocky Mountains to the coast, Clark then follows with a list of the coastal Indians to the north and south of the mouth of the Columbia River. The next item, also from Codex I and in Clark's hand, names tribes from the coastal region east toward the Rocky Mountains and appears to supplement the other list and account for additional tribes. The numbers to the side of the Indian tribal names appear to represent an attempt to bring some order to the multiple lists. This may have been done in preparation for the final estimate, called a supplement by Clark at the end of the second document; the supplement is here printed as the third item. Perhaps as a precaution to losing Codex I and as a preliminary to the supplement, a final list was made and arranged under the numbering system. This list was placed in Voorhis No. 4, clearly a compilation of the lists in Codex I, but set up under the numbering system with adjustments in tribal populations. The combined version of Voorhis No. 4 may be the one referred to on June 13, 1806, or that reference may be to the supplement. Lewis's and Clark's lists from Codex I are printed here with footnotes explaining the differences in Voorhis No. 4.
Two additional items are related to lists of Indians of this later period. Both are in Clark's hand and are loose sheets in the Voorhis Collection of the Missouri Historical Society (see Appendix C). One is titled "Indian Names" and appears to be a preliminary list of Indian tribal names but with no additional comments. Another, single sheet is titled, "A List of the Nations and tribs of Indians residing West of the Rocky Mountains &c." Clark there lists the following tribes, giving some marginal comments very similar to those in the lists below: Clat Sops, Chnnooks, Wau-ki-e-coms, Cath-lah-mahs, Skellutes, Cal-la-mah's, and Quath-lah-pottles.