Because of these limitations on the reliability of informants, most of our work was by necessity based on ethnohistoric research. Every attempt was made to examine the most important literature on the area and period. The total number of sources scrutinized far exceeded the bibliography at the end of this monograph, for many of them contained data that were at best scanty and superficial and at worst totally false. Despite our best efforts to approximate an adequate historical criticism, some of the data presented were found in works that can be used only with great caution. Alexander Ross, for example, has reported much material of doubtful authenticity, and one may labor long and hard in the accounts of Jim Beckwourth to separate fact from a delightful tendency to make the story exciting and his own personage more impressive. It is a wry commentary on the veracity of the mountain men that John Coulter's account of Yellowstone Park was long laughed at by his own peers as being simply an addition to a snowballing folklore of the fur country. Among other dubious sources, we can add W. T. Hamilton and the Irving account of Captain Bonneville's adventures. The problem of criticism becomes particularly difficult during the fur period from about 1810 to 1840 owing to the paucity of sources available for cross-checking particular data. Bonneville and Ross are especially rich in information, most of which cannot be easily verified. The choice became one of dismissing them altogether or using them. We elected to use them, but we have attempted restraint in drawing any important conclusions from them. The monograph follows substantially the report submitted to the Indian Claims Commission. It has been edited, and we have also shifted emphasis at certain points to our own special interests. These are concerned with the relations between the social groups of the Basin and those of the Plains and the impact of the ecology of either region upon the social structures of the native population. A few qualifications should be noted. The limitations imposed by our assignment and by time did not allow the collection of as full a range of material on social structure as would be wished. Also, we have excluded any discussion of the Shoshone of Nevada, for our field work there was far too brief. Our one week at Duck Valley only served to reinforce our opinion of the truly masterful ethnography represented by Steward's "Basin-Plateau Aboriginal Sociopolitical Groups," and we could add little to his work.