Initially I was going to include Tumamoc Hill in my book. I even wrote nearly 1,000 words about it. I later decided to cut the chapter because Tumamoc Hill's location in the Tucson Mts. is hardly a wilderness area, and the University of Arizona and State Land Department, which own the mountain, probably don't appreciate the public tromping up and down its slopes. Anyway, compared to other sites in the book, there isn't a whole lot to see on Tumamoc Hill today. It has been studied extensively, though, making it an important site from an academic point of view. The following chapter was written before I decided to kill it completely.

Cero de Trincheras
As the name implies, Tumamoc Hill is a hilltop ruin. However, this place differs quite a bit from most other Hohokam hilltops. It falls into special category of ruins called cero de trincheras, or entrenched hills, which occur throughout southern Arizona and the Mexican states of Sonora and Chihuahua.

One of the most notable differences between trincheras and other hilltop sites is the sheer size of the ruins. Rather than consisting of, say, a small stone pueblo at the top of a hill surrounded by a single wall, trincheras usually have a whole series of rock walls that lay one after another from the peak of a mountain all the way to its base. In some cases the ruins cover mountains so completely that the walls look more like terraces for agriculture. Most trincheras were built between A.D. 1100 and 1300.

A Mile of Walls
At the Tumamoc Hill trinchera, the best-preserved walls lay on the east and west slopes of the mountain. Most of the crumbling old walls stand only 1 to 3 feet tall, but they’re still massive enough and numerous enough to add a mysterious ambiance to the mountain. Archaeologists have determined that if you linked all the walls together in a straight line, the great rock structure would stretch for more than a mile.

Like so many aspects of Hohokam architecture, the purpose of the trincheras remains unclear. The archaeologist David R. Wilcox observed many characteristics about the walls that led him to conclude they were constructed for defense. For one thing, the walls only exist on gentle slopes where access to the summit is easy. The Indians apparently saw no need to enhance protection in areas already blocked by cliffs or natural boulder outcrops. In addition, the ground just above the walls is always flat and clear while the ground below is covered by a revetment of loose rock rubble that slopes away from the walls. This would have given defenders on the uphill side a distinct advantage in terms of mobility and solid footing. Wilcox used several other findings to support his conclusion, but these are the most obvious.

Evidence that trincheras were used for defense can also be found in the writings of an early Spanish explorer. From 1693 to 1701, Juan Mateo Manje, a military Captain, made a series of trips through Arizona and Sonora with Father Eusebio Francisco Kino, a Jesuit who wanted to establish missions among the Pimas and other Indians in the region. During Manje’s travels, he passed by a trinchera near the Santa Magdalena River in Sonora. The local Pimas explained the odd site to the Captain, prompting him to write the following passage in his journal:

Note that Manje refers to "former" wars, indicating that the fighting took place in prehistoric times (before the arrival of Europeans). Being that the Pimas are probably descendants of the Hohokam, it does not seem unreasonable to conclude that the Hohokam, who lived only a few centuries before Manje's expedition, did as their later relatives apparently did and used their trincheras to fall upon their enemies and kill them.

It should be noted, though, that more recent research suggests trincheras in general were used for a variety of purposes other than defense. Christian E. Downum, Paul R. fish and Suzanne K. Fish found that the slopes of trincheras have microclimates that discourage frost, and that the rock “walls” absorb heat during the day a radiate it back into the ground at night. The warmer temperatures on the trincheras would have made their slopes better places to grow crops than the desert floor, and the Indians may have done just that. The researchers also found evidence that the Hohokam used trincheras in southern Arizona for habitation and ceremonial purposes. Perhaps the only thing certain about Tumamoc Hill is that the function of its walls remains uncertain.

Pictures From the Past
There is, by the way, more on Tumamoc Hill than ancient walls. Rock art depicting people, animals, abstractions and geometric patterns can be found on cliffs and large boulder outcrops.

According to a report by Alan Ferg, a researcher who surveyed all the artwork on the mountain, Tumamoc Hill contains more than 460 petroglyphs. Ferg’s interpretation of the glyphs is simple: Their primary purpose was decoration. The ancients just thought they looked nice, much like modern Americans think paintings enhance their living room walls. Making petroglyphs for decoration also would have been a good creative outlet and may have enhanced the status of those who made them well. This theory is totally improvable, but it has a special appeal in that it assumes prehistoric Indians, like modern Americans, were ordinary people and did not attach profound religious or ceremonial meaning to every single thing they did.

Prehistoric Blenders
At the summit of Tumamoc Hill are some perfectly round holes bored into large, flat boulders. These are mortars. The Hohokam placed food in the small rock cavities and ground it up using hand-held stones, or pestles. Most likely the Indians used these tools to process mesquite and palo verde beans, although the holes look like they could have been used to chop, grate, grind, stir, puree, mix, whip, blend, frappe or liquefy just about anything.