You might be among the 46 million people who've seen a video showing how wolves changed Yellowstone, or you may have heard another version of the story. Yellowstone, which covers nearly 3,500 square miles (9,100 square kilometers) of the western United States, was the world's first national park. It s pioneering reintroduction of wolves, which began in 1995, set a worldwide precedent for conservation. ...read more read less