Historically, there were 20 to 30 million of these animals in North America. Often called buffalo, they are really American Bison. You might think they are like large, shaggy cows, but a full-grown bison can weigh over 2000 pounds. One late evening in Yellowstone National Park, we were driving back to our camp, when we encountered a herd of bison walking down the road. We were stopped by the bison as they slowly walked past our truck. I had my window down and as they came by, inches from the truck, I rolled it up and we sat there petrified, hoping that none of these huge creatures took a mind to pushing us over.