About 1.25 million years ago, a spectacular volcanic eruption created the 13-mile-wide circular depression now known as the Valles Caldera, located in northern New Mexico. This revised & expanded edition marks the twentieth anniversary of the Valles Caldera Preservation Act, a visionary piece of legislation that transferred to the public domain a privately owned ranch (signed in 2000 by President Bill Clinton). The preserve was assigned to a board of citizens appointed by the president to manage it as a self-sustaining preserve. The experiment in semi-private land management ended in 2014 as the Valles Caldera was legislatively reassigned to the National Park Service.