Book excerpt: Galen Cranz surveys the rise of the park system from 1850 to the present through 4 stages - the pleasure ground, the reform park, the recreation facility and the open space system. Looking at both their physical design and social purpose, Cranz argues that city parks have become an instrument of social policy with the potential for reflecting and serving social values. Galen Cranz is Associate Professor of Sociology in Architecture at the University of California, Berkeley