James Johnston, a forty-niner from Ohio, established a homestead on this wild, romantic vista of sloping fields and ocean shore in 1853. For his Californiano [sic] bride, Petra Maria de Jara, he built this typical eastern saltbox, whose origins from the American colonial period date back to medieval East Anglican architecture. Rare in California, this "New England farmhouse" is the earliest American home still standing along the coastside of San Mateo County. Its handhewn redwood timbers form a link with the past when San Benito or "Spanishtown" consisted of a few adobes. The small chapel on the second floor and the separate cookhouse reflect the influence of its Spanish mistress and make the transplanted house uniquely Californian. Known as "The White House of Half Moon Bay," it was the center of the social and cultural life of its day. The history of the house and the Johnston family is a history of a pioneer period of the American West.

In recognition of its preservation for future generations by the Johnston House Foundation, Inc., the Spanishtown Historical Society, and the City of Half Moon Bay, this plaque was dedicated on May 14, 1976 by the American Revolution Bicentennial Committee of San Mateo County.

Quoted from an interpretive marker at the site.

The Peninsula Open Space Trust (POST) completed its purchase of the 862-acre Johnston Ranch from private owners in 2001 for $5.65 million. Until the time of POST's purchase, various owners of the property had plans to develop estate homes, a hotel and golf course.

POST's purchase will:

• unify the historic Johnston Ranch and maintain the spectacular pastoral landscape south of Half Moon Bay
• Preserve the open hillsides and farmland surrounding the landmark Johnston House, built in the 1850s
• protect land farmed by a local family since 1949
• create the opportunity for future parkland and trail corridors extending from Skyline Blvd. to Half Moon Bay
• protect vital habitat for the federally-listed threatened steelhead trout and California red-legged frog

Quoted from a POST interpretive marker at the site.