We describe the distinguishing physical characteristics of old ponderosa pine trees in the Front Range of Colorado, the processes that tend to preserve them, their past and present ecological significance, and their role in ecosystem restoration. Photographs illustrate identifying features of old ponderosa pines and show how to differentiate them from mature and young trees. The publication includes a photographic gallery of old ponderosa pine trees growing on poor, moderate, and good sites. We illustrate trees growing under various forest conditions and with different injuries and histories. We discuss dendrochronological methods of aging old trees and determining their fire history. The companion field guide includes a condensed description of ponderosa pine ecology, distinguishing characteristics of old ponderosa pines, and a photographic gallery illustrating their identifying features.