Julian and Edna Bloss Thorne developed the land in the 1920s, building a house designed by Gardner Daily and surrounding it with extensive gardens. Those gardens included a small lake named after the neighboring Schilling estate -- the Schilling of August Schilling & Company, the San Francisco spice merchants. Both the Thorne and Schilling properties were carved from Rancho Canada de Raymundo, one of the Mexican-era land grants that preceded American California. The landscape retains traces of these layered histories: the rancho, the estates, and now the public preserve.

The preserve is small -- 1.5 miles of trails open to hikers and equestrians, and dog-friendly. The Schilling Lake Trail leads to the lake, a protected wildlife habitat, offering brief views of the southern San Francisco Bay, Palo Alto's Hoover Tower, and the Diablo Range before ducking into second-growth redwood forest. In 2005, the district approved a $1.2 million plan to eradicate an invasive strain of slender false brome that was displacing native plants -- a reminder that even protected spaces require active management to remain what they are.

In 1986, Robert Procter and his wife donated an additional 3.4 acres, expanding the preserve slightly. Thornewood remains one of the smaller open spaces in the Midpeninsula District's system, but its story -- a private estate transformed by bequest into permanent public land -- captures something essential about the Peninsula's conservation ethic. In a region where land values are measured in millions per acre, the decision to leave a hillside undeveloped is itself a kind of defiance.