The dwellings of these various tribes had a great deal of variety. It was popularly supposed for many years that an "Indian" lived only in a skin tent or a wickiup, or any shiftless kind of a shelter, consequently when it was discovered that there were some who had lived centuries ago in rather well constructed houses which were found in ruins, it was assumed that these people must have been of another race and a superior one. The fact that tribes were still building and occupying houses of the same kind, who were only common "Indians," was not for years permitted to interfere with the romance, but now the "vanished-race" theories are pretty well abandoned except perhaps by visionary writers who do not understand the field. The ruins were found in canyons and valleys where natural-rock _débris_ and a poverty of timber and large skins almost compel house-building. A vast abundance of gypsiferous clay furnished another excellent building material, for that climate, and this was utilised in the South-west where other materials were difficult to secure. They also rammed this clay mixed with gravel into large wicker frames which were lifted, after the mass had hardened, to aid in preparing other blocks on top, so that a sort of clay concrete-block wall was raised. When the white men first came to the country, a ruin of one of these large houses called _Casa Grande_ stood in Arizona near the present town of Florence. No one knows when this structure was erected or abandoned. It is still standing about as first described by whites. The government has assumed its care and protection. [Illustration: Ruin Called Casa Grande, Arizona. Photograph by Cosmos Mindeleff, U. S. Bu. of Eth.] The Mandan built a large round earth-covered wigwam which was substantial and comfortable. The Dakota developed the portable tipi. The Shoshone lived in skin tents and huts of boughs, as did the Comanche. The tribes of the North-west built strong houses of slabs, often very long. The tribes of California built of brush and slabs. Each people constructed a habitation in accordance with the facilities of the region they occupied, and while house-building may indicate a certain superiority of social advancement it is no mark of race differentiation. Tribes of one stock built good houses and lived in mere brush shelters at the same time. Some of the occupied villages became of great importance in the early days of white intrusion, notably Taos, a pueblo on the headwaters of the Rio Grande. This figured prominently in the events which broke the Wilderness from the time of Espejo to the acquisition of the region by the Americans, and is standing to-day.