From their advance in house building, it has been commonly stated that the Pueblo people were either derived from Mexican tribes or, as was customary in the seventeenth and eighteenth centuries to suppose, their descendants had made their way south and developed into the more advanced Mexican culture as the Aztecs. These conclusions are not supported by comparison with available architectural data observed among these two peoples. The basal error is the mistake in considering the earth houses of the Gila the same as pueblos. The habitations of the Gila compounds were structurally different from pueblos, and their sanctuaries or ceremonial rooms had not the same form or relation to the dwellings. The Gila compounds are allied to Mexican buildings; but there is little in common between them and pure pueblos. The same is true of the type of stone dwellings on the Verde, Tonto, and Little Colorado. Certain likenesses exist between the Casas Grandes of the Gila and those of Mexico, although little relationship exists between the temples or ceremonial buildings of the valley of Mexico and the Casas Grandes of the Gila. The architecture of the Pueblos and the Aztecs is very different; the habitations of Mexican tribes resemble those of the Gila. The forms[55] of ceremonial chambers differ, one being rectangular mounds or pyramids, the other circular, generally subterranean. [55] Temples of Quetzalcoatl, the Plumed Serpent Sun God, are circular buildings like towers. Rather than seek the origin of the house builders of the San Juan, or the parent Pueblos, from Mexican sources, the author believes the custom of building stone houses in the pueblo region was not derived from any locality not now included in the pueblo area, but it developed as an autochthonous growth, the earliest stages as well as the most complex forms being of local origin. Incoming Indians may have introduced ideas of foreign birth but they did not bring in the mason’s craft. That custom developed in the Southwest, where we find the whole series from a single stone-house or a cave with walls closing the entrance to the most highly developed architectural production north of Mexico. There are cliff-dwellings in many other localities in the world but there are nowhere, except in the region here considered, cliff-dwellings with circular kivas constructed on this unique plan. It is generally supposed that a type of room called “small house” was the predecessor of the multiple community dwelling throughout the Southwest. This type, defined as a simple four-walled, one story building with a flat roof, is widely spread in New Mexico and Arizona. The strongest arguments in favor of its greater antiquity are possibly its simplicity of form and the character of accompanying ceramics—corrugated, black-and-white, and red pottery. Characteristic small houses of the Mesa Verde and McElmo Canyon belong to the same type of pueblo as the largest extensive villages which are more