Bison in Yellowstone National Park

We saw lots of them, different herds in different places.  My understanding is that they were nearly completely wiped out, but the herds in Yellowstone are thriving.  They looked docile enough, but there were signs everywhere saying they were dangerous and not to approach them.  This herd was right by the road.

This is the view back the other way.  I had to glance back over my shoulder to make sure a bison wasn't coming my way.