West of Tucson 65 miles is the little town of Casa Grande, which takes its name from one of the most famous prehistoric ruins in the United States, standing about 18 miles to the northeast, near the Gila River. If you have a taste for prehistoric architecture, you will enjoy Casa Grande, for it is _sui generis_ among our country’s antiquities. If, on the other hand, you are just an ordinary tourist, you must decide for yourself whether a half day’s motor trip across the desert to see a ruinous, cubical mud house topped with a corrugated iron roof, in the midst of a sunburnt wilderness, will or will not be worth your while. What touches the fancy is that here, centuries doubtless before Columbus (perhaps before the time of the Cliff Dwellers) dwelt and toiled an unknown people whose remains are of a type that possesses important points of difference from those found elsewhere within the limits of the United States, though similar ruins exist in Mexico. Casa Grande is Spanish for Great House, and is given to this ruin because its outstanding feature is a huge block of a building of three or four stories in height, and thick walls of _caliche_—a mixture of mud, lime and pebbles molded into form and dried, somewhat as modern concrete walls are built up. The unique character of the Casa Grande caused it to be set aside 25 years ago as a National Monument, and important work has since been done there by Government ethnologists, in the way of strengthening and repairing the crumbling walls and cleaning up the rooms. Extensive excavations have also been made close by, resulting in uncovering the foundations of a numerous aggregation of houses plazas, enclosing walls, etc. These reveal the fact that in some age the place was a walled city of importance, even if it was of mud—a sort of American Lutetia, to which Fate denied the glory of becoming a Paris. The huge building in the center—the Casa Grande—probably served partly as a religious temple, but principally as a citadel where in time of attack by enemies the people took refuge. Access to the upper stories was doubtless by ladders outside, as in modern pueblos. Indeed, this is but one of several walled-in compounds of buildings that formerly existed in the Gila Valley, and are now but shapeless heaps of earth. Some of these close to the main Casa Grande ruin have been excavated and their plan laid bare. The remains of an extensive irrigation system are still in evidence, water having been drawn from the Gila.