This is one of two different places with teepee rings on one of my dad's pasture land. My dad has owned the land for about 15 years but it has been in the family for about 50 years. My Dad's grandma remembered hiding behind her mom's skirts as a small child watching the Indians going by with their travois to their summer grounds a few miles away from my dad's great grandparents homestead (which would have been at least 100 years ago). The rings themselves have been their for hundreds of years because the Indians would travel back to the same places. The rings are on top of the hills to catch the summer breezes and to keep the mosquito's away. There are also smaller rings from fire pits and if you dig down into them, you will find bones of small animals. We've found bits of pottery and beads as well.
A direct lift from Henri Jeans LO:http://www.scrapbook.com/galleries/392681/view/3825421/-1.html