These trincheras somewhat resemble the small terrace gardens of the Moqui Indians, and have undoubtedly been used for agricultural purposes, just as they are used by the Tarahumares to this day (page 152).  It is true that they are built in great numbers, sometimes in localities that would appear unsuitable for farming; but, on the other hand, they are seldom, if ever, found far from the remains of habitations, a fact from which it may also reasonably be inferred that the ruined houses, as well as the trincheras, were originally built by the same race.  Some of the terraces were, no doubt, erected as a protection of the crop against enemies and wild animals; but it is impossible to think that they were intended for irrigation dams, though we did see water running through some, coming out of a marsh.  Still less likely is it that they had been used as mining dams.

As soon as the plains of Northern Sonora were left behind, and the country became hilly and broken, these peculiar structures were conspicuous.  At first they appeared more like walls built simply along the slopes of the hills, and not crossing gulches.  They seem to be more numerous in the western and central part of the sierra, its spurs and foot-hills, than in the eastern part of the great range.  As regards their southern extent, they are not found further south than the middle part of the state of Chihuahua.  Captain Bourke, in his book, “An Apache Campaign,” mentions that “in every sheltered spot could be discerned ruins, buildings, walls, and dams, erected by an extinct race once possessing these regions.”  Mr. A. F. Bandelier, on his journey to the Upper Yaqui River, in 1885, which took him as far as Nacori, also refers to them, and Professor W. J. McGee, on his expedition in 1895, found in Northeastern Sonora ruins locally known as Las Trincheras, which he considered the most elaborate prehistoric work known to exist in Northwestern Mexico.  They comprise, he says, terraces, stone-walls, and inclosed fortifications, built of loose stones and nearly surrounding two buttes.

I must not omit to mention that in a week’s exploration in the mountains near Nacori, Mr. Stephen and his party did not find any pottery fragments, nor flint flakes, nor grinding stones.  They reported that there was in that region no other trace of an early people than the hundreds of trincheras in the lower portions of the arroyos.

Noteworthy, however, was the frequent occurrence of old trails across the hills, some quite plainly traceable for three and four hundred yards.  Old oaks stretched their limbs across many of them quite close to the ground.