European settlers to the New World in the 19th century coined the term "medicine wheel" to refer to the many stone features they observed on the northwestern plains. In 1885, surveyor George Dawson made the first published account of them in an article entitled the "Geological and Natural History of Canada". Where there were about 20,000 medicine wheels in North America then, many of them have been vandalized by tourists and today there are about 135 on and near the Great Plains. Radiocarbon dating has shown some of them to be a few thousand years old, like the 4500 year old Majorville Medicine Wheel, while others were built in more recent centuries. Besides having a central cairn, an outer circle and spokes, some medicine wheels also have extended spokes outside the boundary of the circle reaching up to 120m in length, while others have more than one concentric stone ring. Tipi rings, smaller stone circles, are also found in some of the wheel formations. The wheels are usually found on high ground areas of prominent topographic setting where there is a full, unblocked view of the horizon.
The hypothesized functions of the medicine wheels vary greatly. To the American Indians, medicine wheels on the physical level are believed to be guides to building tipis and Sundance lodges. On the spiritual level they represent creation, with each stone telling part of the story of creation. The circle shape is sacred as the Great Spirit caused everything in nature to be round. The sites are supposedly places of energy, celebration and spiritual reflection. Within the sites are expressed the four cardinal directions and the elements. Other suggested functions of the wheels have included them being oxzemo(spirit wheels) aimed at the sky, the sites of burials, monuments and sites of ceremonial celebrations like the Sun Dance Ceremony. They have even been hypothesised to have been built with connections to celestial observations.
One of these wheels, the Bighorn Medicine Wheel, can be found 10,000 feet above sea level at Medicine Mountain in Bighorn National Forest. It is an American National Historic Site. The closest Native American tribes in the area are the Crow and the Cheyenne. The wheel is a revered spiritual site to them, with many making the trip up to meditate and pray despite the harassment of tourists and park rangers. Some Crow say this wheel was built "before the light came" and others believe it was built by "people without iron" and "dropped from the sky by the Sun God". Dates for the site ranging from 1200 AD and 1700 AD have been dropped from tree ring dating but are tainted with uncertainty. We do not have any concrete answers to the real builders of the wheel, and archaeologists are not clear on it's exact purpose, although findings by Dr John. A. Eddy in the 1970s have given us strong evidence linking it to astronomical symbolism.