Yellowstone - Wyoming
A few rules with bears: Keep a safe distance, a min. of 100 yard , keep close to your car, hiking in a large group, and if an encounter occurs during hiking, avoid surprising a bear, never run away from them or climb a tree (they can outrun and climb faster than you), back off slowly, avoid direct eye contact, try to appear bigger, act like a 600 pound gorilla, carry bear spray, play dead when attacked by bending over face down on the ground with both hands covering your face, head and neck. Park Visitor Centers have bear spray for sale or rent. Get one if you intend on hiking. The distance of spray is 30 feet. Normally bear is aftraid of humans and in the unlikely event of an attack, hit his eyes and nose with anything you have.