Yellowstone National Park, Wyoming, Idaho, Montana, United States

Yellowstone is one of the most popular national parks in the United States. Since the mid-1960s, at least 2 million tourists have visited the park almost every year. In 2010, a record number of visitors came to the park in July: 975,000. July is the busiest month for Yellowstone National Park. At peak summer levels, 3,700 employees work for Yellowstone National Park concessionaires. Concessionaires manage nine hotels and lodges, with a total of 2,238 hotel rooms and cabins available. They also oversee gas stations, stores and most of the campgrounds. Another 800 employees work either permanently or seasonally for the National Park Service.
Park service roads lead to major features; however, road reconstruction has produced temporary road closures. Yellowstone is in the midst of a long term road reconstruction effort, which is hampered by a short repair season. In the winter, all roads aside from the one which enters from Gardiner, Montana, and extends to Cooke City, Montana, are closed to wheeled vehicles. Park roads are closed to wheeled vehicles from early November to mid April, but some park roads remain closed until mid-May. The park has 310 miles (500 km) of paved roads which can be accessed from 5 different entrances. There is no public transportation available inside the park, but several tour companies can be contacted for guided motorized transport. In the winter, concessionaires operate guided snowmobile and snow coach tours. Facilities in the Old Faithful, Canyon and Mammoth Hot Springs areas of the park are very busy during the summer months. Traffic jams created by road construction or by people observing wildlife can result in long delays.
The National Park Service maintains 9 visitor centers and museums and is responsible for maintenance of historical structures and many of the other 2,000 buildings. These structures include National Historical Landmarks such as the Old Faithful Inn built in 1903–04 and the entire Fort Yellowstone - Mammoth Hot Springs Historic District. An historical and educational tour is available at Fort Yellowstone which details the history of the National Park Service and the development of the park. Campfire programs, guided walks and other interpretive presentations are available at numerous locations in the summer, and on a limited basis during other seasons.
Camping is available at a dozen campgrounds with more than 2,000 campsites. Camping is also available in surrounding National Forests, as well as in Grand Teton National Park to the south. Backcountry campsites are accessible only by foot or by horseback and require a permit. There are 1,100 miles (1,800 km) of hiking trails available. The park is not considered to be a good destination for mountaineering because of the instability of volcanic rock which predominates. Visitors with pets are required to keep them on a leash at all times and are limited to areas near roadways and in "frontcountry" zones such as drive in campgrounds. Around thermal features, wooden and paved trails have been constructed to ensure visitor safety, and most of these areas are handicapped accessible. The National Park Service maintains a year round clinic at Mammoth Hot Springs and provides emergency services throughout the year.