Established in 1872, Yellowstone National Park is America's first national park. It is one of the largest active volcanoes in the world. The park covers 3472 square miles and is mostly above 7500 feet. Located in Wyoming, Montana and Idaho, it is home to a large variety of wildlife. Preserved within Yellowstone National Park are Old Faithful and a collection of the world's most extraordinary geysers and hot springs, and the Grand Canyon of the Yellowstone. Here is a selection of images from a winter trip.