By Victor Mindeleff. * * * * * INTRODUCTION. The remains of pueblo architecture are found scattered over thousands of square miles of the arid region of the southwestern plateaus. This vast area includes the drainage of the Rio Pecos on the east and that of the Colorado on the west, and extends from central Utah on the north beyond the limits of the United States southward, in which direction its boundaries are still undefined. The descendants of those who at various times built these stone villages are few in number and inhabit about thirty pueblos distributed irregularly over parts of the region formerly occupied. Of these the greater number are scattered along the upper course of the Rio Grande and its tributaries in New Mexico; a few of them, comprised within the ancient provinces of Cibola and Tusayan, are located within the drainage of the Little Colorado. From the time of the earliest Spanish expeditions into the country to the present day, a period covering more than three centuries, the former province has been often visited by whites, but the remoteness of Tusayan and the arid and forbidding character of its surroundings have caused its more complete isolation. The architecture of this district exhibits a close adherence to aboriginal practices, still bears the marked impress of its development under the exacting conditions of an arid environment, and is but slowly yielding to the influence of foreign ideas. The present study of the architecture of Tusayan and Cibola embraces all of the inhabited pueblos of those provinces, and includes a number of the ruins traditionally connected with them. It will be observed by reference to the map that the area embraced in these provinces comprises but a small portion of the vast region over which pueblo culture once extended.