The diaries, reports, letters, and reminiscences of the Ibero-American pioneers in California from 1770 to 1840 give us primary information for which there is no substitute. In the first place, they fill in the gap in our knowledge of the aboriginal peoples between what is deduced from purely archaeological evidence and what is learned from personal informants whose memories can reach back to a time only a little before the year 1850. Moreover we learn a good deal about the location and behavior of village or tribal groups which were entirely extinguished before the memory of modern survivors. In the second place, we see in detail the initial reaction of the Indian to the Spaniard in the wild environment and witness the subsequent struggle for survival on the part of the native population. In the third place, we obtain firsthand knowledge concerning the primitive environment of the interior, the condition of the land, the character and extent of vegetation, the location and capacity of rivers, swamps, and lakes. Such data antedate the memory and written descriptions of the earliest American observers and so are of great value in tracing the changes which have since occurred. The body of literature under consideration is found in only a few places. Some documents are in the Mexican National Archive, with microfilm possibly available. The largest single collection is in the Bancroft Library at Berkeley, with smaller collections at the Huntington Library and elsewhere. A few of the important diaries are in the form of the original manuscripts or contemporary copies. The greater part of the material, however, consists of transcripts of the originals made at the order of H. H. Bancroft in the 1870's. Despite the very sloppy work done by the paid copyists it is fortunate that the attempt was made, for the documents themselves were nearly all destroyed in the San Francisco fire of 1906.