Above the timberline in the Big Horn Mountains of northern Wyoming exists a massive Medicine Wheel whose pattern of stones etches an imperfect circle with a diameter of about 25 meters. A group of stones about four meters in diameter establishes the hub of the wheel. Twenty-eight "spokes" angle out from the hub and connect with the outer rim. The Big Horn Mountains was significant to the Crow, the Sioux, the Arapaho, the Shoshone, and the Cheyenne Indians—but none of these tribes were known for building stone monuments. Bits of wood found in one of the six smaller groups situated unevenly about the rim indicates that the Medicine Wheel has been there since at least 1760 and was likely constructed around 1700. The monument has been known to non-natives for over a hundred years, but speculation about its true purposes has only inspired mysteries and tales.
John A. Eddy, a solar physicist and astronomer on the staff of the High Altitude Observatory, National Center for Atmospheric Research, in Boulder, Colorado, became interested in the site, especially after he discovered a large, crude pile of stones oriented to the summer solstice sunrise at over 11,000 feet on the Continental Divide. Interested by this discovery, he wanted to investigate just how much the pre-contact native people might have known of astronomy, and it occurred to him that the wheel might have been an observatory. Research over two summers on the site convinced him that the Big Horn monument may have been a primitive astronomical observatory that served its creators at least as well as Stonehenge served its primitive astronomers. The high altitude (9,640 feet) and the clear horizons of the monument make visible the marking of sunrise and sunset at the summer solstice. The accurate knowledge of the first day of summer would have been an important for a nomadic people whose lives depended on awareness of seasonal changes.
Giese, Paula. "Stone Wheels and Dawn Stars Rising." [Online] http://www.kstrom.net/isk/starskno7.html.
Thomas, David Hurst. Exploring Ancient Native America. New York: Macmillan, 1994.