A historic resources survey was completed in 1983 for the entire area included in the original Rancho Sotoyome Mexican land grant, and included 339 properties and 6 districts within the City of Healdsburg. Approximately 2/3 of the properties were subsequently assigned a California Historical Resources Status Code. The State Office of Historic Preservation determined that most of the remaining properties needed to be re-evaluated before a code could be assigned. The 1983 survey was subsequently used to designate the Johnson and Matheson Street historic districts.
A Historic District (H-D) Overlay may be applied to areas of the city that are of historic significance or contain significant historic structures, as well as to individual properties with historically-significant structures in order to preserve, maintain and enhance their historic integrity. The adoption of a historic designation for an individual property or a group of properties within a district requires a Zoning Map Amendment applying the HD Historic Overlay District to each of the properties.