From the new shelton wet/dry:
American Indians used to chase buffalo over a cliff. The cliff was called a buffalo jump. The most famous of Wyoming’s buffalo jumps is the Vore Buffalo Jump located near Beulah. From the layers of bones, scientists have estimated that some 20,000 bison were killed at the site and that it was in use as late as 1800 AD.
Update 2/22/07: The buffalo photo above is by David Wojnarowicz - Thanks Jullian Miller!