Explores the US National Park Service's (NPS) attempt to achieve "sustainability" - a balance that allows as many people as possible to visit a park that is kept in as natural a state as possible. O'Brien details methods the NPS has used to walk the line between those who would preserve vast tracts of land for "no use" and those who would tap the Yellowstone geysers to generate electricity. His case studies of six western "crown jewel" parks show how rangers and other NPS employees are coping with issues that impact these cherished public landscapes, including visitation, development, and recreational use.