Established in 1872, Yellowstone National Park is the oldest and one of the largest national parks in the world. In this book, scientists Mary Meagher and Douglas B. Houston present one hundred sets of photographs that compare the Yellowstone of old with the park of today. Through close analysis of the photos and reference to the vast amount of available data, Meagher and Houston describe changes in vegetation, growth of wildlife populations, the effect of beaver occupancy on wetland areas, and geothermal and elevational shifts. At the same time they point out the extent to which many sites have not changed - despite important switches in park policy and an increase in human activity. This book will be of value to scientists from various disciplines as well as to the many people who care about Yellowstone and other protected wilderness areas around the world.