On Interstate 10 between Tucson and Phoenix is one of America's most enduring ancient mysteries--a giant adobe structure called Casa Grande. It was erected by the Hohokam, a people who built towns where Tucson and Phoenix are today and who turned the desert green with an extensive system of irrigation. Ironically, the modern city of Phoenix was founded by American settlers who cleared out the prehistoric Hohokam canals and reused them for their own farms.

Casa Grande was a settlement between these two centers of population and was at its height 150 years before Columbus "discovered" America. At its center was a four-story building unlike anything else in the prehistoric southwest. Nobody knows for sure why the Hohokam civilization died out shortly thereafter, and nobody knows the purpose of Casa Grande. The late archaeoastronomer Dr. Ray White believed that Casa Grande's windows were a prehistoric observatory that marked important times in the calendar such as the solstice and the equinox.

This mysterious building became the nation's first archaeological preserve in 1892 and a national monument in 1918. Archaeologists have since realized the monument doesn't protect many outlying areas of the site, and now Rep. Ann Kirkpatrick (Dem-1st District) has proposed House Resolution 5110 to protect 415 more acres. The move has the support of local archaeologists as well as the influential newspaper The Arizona Republic. The expansion was initially proposed by Kirkpatrick's Republican predecessor Rep. Rick Renzi.

It's a gutsy move at a time of belt tightening and threatened park closures, so it will be interesting to see if a destination on the itinerary of so many southwestern road trips will get the funds to expand its boundaries.

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