In many respects Casa Grande ruin is one of the most noteworthy
relics of a prehistoric age and people remaining within the limits
of the United States. It was discovered, already in a ruinous
condition, by Padre Kino in 1694, and since that time it has been a
subject of record by explorers and historians. Thus its history is
exceptionally extended and complete. By reason of its early
discovery and its condition when first seen by white men, it is
known that Casa Grande is a strictly aboriginal structure; and
archeologic researches in this country and Mexico afford grounds for
considering it a typical structure for its times and for the natives
of the southwestern region. Many other structures were mentioned or
described by the Spanish explorers, but the impressions of these
explorers were tinctured by previous experience in an inhospitable
region, and their descriptions were tinged by the romantic ideas of
the age; very few of these structures were within the limits of the
United States, and nearly all of these situated in the neighboring
republic of Mexico disappeared long ago; there is hardly a structure
left, except Casa Grande ruin, by which the early accounts of
Spanish explorers in North America can be checked and
interpreted--none other of its class exists in the United States.
Casa Grande ruin is, therefore, a relic of exceptional importance
and of essentially unique character.

Unfortunately this structure, like others erected by the most
advanced among the native races in the southwest, is of perishable
material; it is built of adobe, or rather of cajon, i.e., of a
puddled clay, molded into walls, dried in the sun. Such walls would
stand a short time only in humid regions; but in the arid region the
material is desiccated and baked under cloudless sky and sun for