James P. Johnston was born in Scotland in 1813 and came to the United States as a child, growing up in Gallipolis, Ohio. By the early 1850s he had reached California, and in 1852 he married Petra Maria de Jara, a young woman from an established Californio family. Johnston purchased 1,162 acres of the southern sections of Rancho Miramontes, land once held by Candelario Miramontes, and set about building a dairy farm. The house he constructed between 1853 and 1855 was remarkable for its location: a New England-style saltbox design built from hand-hewn redwood timbers, the first wood-framed structure on a coast where adobe and hide had been the building materials of choice. Petra died in 1861 at just twenty-eight. Johnston struggled financially and eventually sold most of his land, but the house endured.

The Johnston House entered the National Register of Historic Places on May 9, 1973, a recognition that came just in time. The city of Half Moon Bay acquired the property in 1975, and renovations began the following year with help from the Spanishtown Historical Society and the newly formed Johnston House Foundation. Then came the windstorm of November 1976, reducing the house to a heap of old wood. The reconstruction that followed was as much an act of community will as architectural restoration. Workers reassembled the hand-hewn redwood timbers, this time setting them on a concrete foundation for stability. A new chimney was added. The result is not a pure restoration but something more honest: a building that carries its history in its bones while acknowledging that survival sometimes requires adaptation.

The Johnston House now serves as a museum furnished with era-appropriate pieces and Johnston family memorabilia donated by descendants. But the story extends beyond the house itself. In January 2001, the Peninsula Open Space Trust purchased the surrounding 862-acre Johnston Ranch to protect the land from development, ensuring that the pastoral landscape Johnston knew in the 1850s would remain open. The ranch purchase connected the house to a broader conservation effort along the San Mateo coast, where development pressure from nearby Silicon Valley communities has made open space increasingly precious. The White House of Half Moon Bay is small, rebuilt, and not entirely original -- but it is still standing, which is more than can be said for most things built on this coast 170 years ago.