Website:
http://www.lewisandclarktrail.com/section3/montanacities/greatfalls/ulmpishkun/ (Website)

Description:
For more than 1,000 years, prehistoric men and women of the Great Plains hunted bison by driving them over cliffs. Ulm Pishkun, is possibly the largest buffalo jump in the world, was used as a jump site between 900 and 1500 A.D. Below the cliffs that stretch more than a mile, the soil reveals compacted bison bones nearly 13 feet deep.