[6][3][10] After the purchase of land, Johnston began building the first wood-framed house along the San Mateo County coast, using a New England–style “saltbox” design.

[5] The house had clear Spanish influence and featured a Roman Catholic chapel (something commonly seen in Californios homes) and an open gallery facing a patio.

[3] Food was prepared in a free-standing kitchen outside of the house, possibly to reduce odors or because of social factors with feeding many farm hands and/or having a Chinese cook.

[3][4] Petra's mother, Ursula Melita Valenzuela de Jara and James's sister Isabel Johnston moved into the house to raise three of the children.

[6] In 1916, Angelo Cassinelli bought the property and grew brussels sprouts on the land, and the house was mostly uninhabited since it had no plumbing or electricity.

[13] Preservationists in the area discovered Watkins’ monograph and formed the Johnston House Foundation, Inc..[4] Spanishtown Historical Society helped with the project.

[4][13] In January 2001, the Peninsula Open Space Trust (POST) purchased the 862-acre Johnston Ranch in order to protect the land from development.