In pursuance of a general plan involving the production of a series of works on the western half of North America, I present this delineation of its aboriginal inhabitants as the first. To the immense territory bordering on the western ocean from Alaska to Darien, and including the whole of Mexico and Central America, I give arbitrarily, for want of a better, the name Pacific States. Stretching almost from pole to equator, and embracing within its limits nearly one tenth of the earth's surface, this last Western Land offers to lovers of knowledge a new and enticing field; and, although hitherto its several parts have been held somewhat asunder by the force of circumstances, yet are its occupants drawn by nature into nearness of relationship, and will be brought yet nearer by advancing civilization; the common oceanic highway on the one side, and the great mountain ramparts on the other, both tending to this result. The characteristics of this vast domain, material and social, are comparatively unknown and are essentially peculiar. To its exotic civilization all the so-called older nations of the world have contributed of their energies; and this composite mass, leavened by its destiny, is now working out the new problem of its future. The modern history of this West antedates that of the East by over a century, and although there may be apparent heterogeneity in the subject thus territorially treated, there is an apparent tendency toward ultimate unity. To some it may be of interest to know the nature and extent of my resources for writing so important a series of works. The books and manuscripts necessary for the task existed in no library in the world; hence, in 1859, I commenced collecting material relative to the Pacific States. After securing everything within my reach in America, I twice visited Europe, spending about two years in thorough researches in England and the chief cities of the Continent. Having exhausted every available source, I was obliged to content myself with lying in wait for opportunities. Not long afterward, and at a time when the prospect of materially adding to my collection seemed anything but hopeful, the _Biblioteca Imperial de Méjico_, of the unfortunate Maximilian, collected during a period of forty years by Don José María Andrade, litterateur and publisher of the city of Mexico, was thrown upon the European market and furnished me about three thousand additional volumes.