Yellowstone is a huge park covering over 3,400 square miles in Wyoming, Montana and Idaho. You can reach there by air to Cody or Jackson, 50 miles from the entrances (入口). There is no train service nearby.
Limited (有限的) bus service is used from some of the towns near it. So when you are in the area, a car is a must. The park has 5 entrances and the entrances are open from May to October. It is a good idea to plan a trip during the good weather. And parts of the park are open in winter for snow sports.
Be sure to prepare for different weather at any time of the year. Take enough clothes because the temperature is changeable(多变的).Take good walking shoes and thick socks, if you are going to hike. You can also see the park on horseback.
lf you want to learn about Yellowstone, there are many talks, films and tours to help you to understand it at the National Park Service.