San Francisco's Bernal Heights is a hilltop village tucked away in the southern part of the city. Freeways and urban thoroughfares now bound the neighborhood, once defined by the swamps and creeks of the original Mexican land grant. The legacy of Potrero Viejo, or "old pasture," and the farms of the 19th and 20th centuries have developed into today's passion for the preservation of open space. From the 1860s legend of Widow O'Brien's cow to the 1970s fight that saved the hill's crest from development, Bernal residents have tirelessly guarded their environment.