The remains of pueblo architecture are found scattered over thousandsof square miles of the arid region of the southwestern plateaus. Thisvast area includes the drainage of the Rio Pecos on the east and thatof the Colorado on the west, and extends from central Utah on the northbeyond the limits of the United States southward, in which direction itsboundaries are still undefined.The descendants of those who at various times built these stonevillages are few in number and inhabit about thirty pueblos distributedirregularly over parts of the region formerly occupied. Of these thegreater number are scattered along the upper course of the Rio Grandeand its tributaries in New Mexico; a few of them, comprised within theancient provinces of Cibola and Tusayan, are located within thedrainage of the Little Colorado. From the time of the earliest Spanishexpeditions into the country to the present day, a period covering morethan three centuries, the former province has been often visited bywhites, but the remoteness of Tusayan and the arid and forbiddingcharacter of its surroundings have caused its more complete isolation.The architecture of this district exhibits a close adherence toaboriginal practices, still bears the marked impress of its developmentunder the exacting conditions of an arid environment, and is but slowlyyielding to the influence of foreign ideas.The present study of the architecture of Tusayan and Cibola embraces allof the inhabited pueblos of those provinces, and includes a number ofthe ruins traditionally connected with them. It will be observed byreference to the map that the area embraced in these provinces comprisesbut a small portion of the vast region over which pueblo culture onceextended.This study is designed to be followed by a similar study of two typicalgroups of ruins, viz, that of Canyon de Chelly, in northeastern Arizona,and that of the Chaco Canyon, of New Mexico; but it has been necessaryfor the writer to make occasional reference to these ruins in thepresent paper, both in the discussion of general arrangement andcharacteristic ground plans, embodied in Chapters II and III and in thecomparison by constructional details treated in Chapter IV, in orderto define clearly the relations of the various features of puebloarchitecture. They belong to the same pueblo system illustrated by thevillages of Tusayan and Cibola, and with the Canyon de Chelly groupthere is even some trace of traditional connection, as is set forth byMr. Stephen in Chapter I. The more detailed studies of these ruins, tobe published later, together with the material embodied in the presentpaper, will, it is thought, furnish a record of the principalcharacteristics of an important type of primitive architecture, which,under the influence of the arid environment of the southwesternplateaus, has developed from the rude lodge into the many-storiedhouse of rectangular rooms. Indications of some of the steps of thisdevelopment are traceable even in the architecture of the present day.The pueblo of Zuñi was surveyed by the writer in the autumn of 1881with a view to procuring the necessary data for the construction of alarge-scale model of this pueblo. For this reason the work afforded arecord of external features only.