Bison are large, powerful mammals, that used to roam the entire middle part of the country with impunity.  However they are a fairly docile animal, and were hunted extensively in the late 1800's-early 1900's, to the point that if you want to see one today, you have to go to certain locations.   Yellowstone is home to the most "wild" bison in the USA, with around 5,000 bison.  For the most part, Bison will ignore you, but keep your distance.  These things are big, fast, and you don't want them charging.   Otherwise, head out and watch them.   You can just feel the power as they lumber along, eating their grass and moving their massive heads.