The National Park Service defines a historic district as a “significant concentration, linkage, or continuity of sites, buildings, structures, or objects, unified by past events or aesthetically by plan or physical developments.”  This means that historic districts have numerous components that, when considered together, represent the social, cultural, economic, and/or architectural history of a community.  Individual properties within a district may not be able to express those same patterns when viewed on their own. Historic districts can take many forms. In communities like San Mateo, historic districts often are groupings of buildings in a commercial area—such as the Downtown Historic District—or homes in a residential neighborhood, such as the Glazenwood Historic District.

When a historic district is first evaluated, the properties within the district boundaries are identified as either contributors or non-contributors. Contributors are the properties that date to the district’s period of significance and still retain enough of their historic character to convey the district’s historically important character. In contrast, non-contributors are not closely connected to the district’s significant historic qualities. This might be because they were built outside of the period of significance, or they may have been altered so much that have lost their connection to the district’s significance.

The number and arrangement of contributors within a district can vary from example to example. In some cases, a district with many non-contributors can still qualify for listing in a historic register, so long as the contributors that do exist are able to convey the district’s significant historical or architectural character.

In addition to contributors, districts have character-defining features. Character-defining features are the physical elements contributors share that allow them to express the district’s significance. Character-defining features can include elements like building and roof forms, exterior materials, window and door patterns, setbacks and lot placement, and landscaping.

Local, state, and federal laws establish different historical registers that have their own designation processes and types of review or protection. Listing in one register does not prevent a district from being listed in another. Some historic resources, including districts, are listed in all three. Note that the different historic registers correspond to the laws that created them, rather than the significance of the resources they include. For instance, the National Register was established by federal law but still contains many properties that have local- and state-level significance, in addition to nationally significant resources. 

San Mateo’s Historic Building Survey completed in 1989 identified two historic districts: the Downtown Historic District and the Glazenwood Historic District. The Downtown Historic District, which is focused along South B Street and 3rd Avenue, has particular importance in the history of San Mateo because it has long served as the city’s commercial heart. It maintains much of its historic character from the early decades of the twentieth century. The residential neighborhood of Glazenwood is a unique early 1920's development of Spanish Colonial Revival homes. Currently, the City’s Historic Preservation Ordinance establishes a review process that applies only to the Downtown Historic District.

The California Register of Historical Resources (California Register) is administered by the State of California Office of Historic Preservation (OHP, sometimes also referred to as the State Historic Preservation Office). For a property to be listed in the California Register, nomination materials are submitted to the local government for comment, and then to OHP for staff review. OHP notifies property owners in the district and then brings the nomination before the State Historical Resources Commission (SHRC), an appointed review body, for a public review hearing. During the hearing, the SHRC votes on whether to approve the nomination. 

The National Register of Historic Places (National Register) is administered by the National Park Service in coordination with state governments. The nomination process for the National Register is similar to the process for the California Register. In California, OHP reviews the completed National Register nomination and notifies property owners before it is heard by the SHRC, who may vote to send it to the National Park Service for final approval. All districts that are formally listed in the National Register are automatically listed in the California Register.

A historic district cannot be formally listed in either the California Register or the National Register over the objection of a majority of property owners. If the SHRC determines that a proposed district is eligible for the National Register, and if a majority of property owners document their opposition, then the nomination would be submitted to the Keeper of the National Register as a determination of eligibility for the National Register, rather than a nomination for listing in the National Register.

Eligible districts do not qualify for certain preservation incentives, such as federal or state tax credits; however eligible districts are treated the same as listed districts with respect to state- and federal-level project review, including for environmental review under the California Environmental Quality Act. Please see the “How to Support or Object” from the State of California Office of Historic Preservation

Owners of properties in historic districts are encouraged to consider their properties’ historic character and develop projects that follow the Secretary of the Interior’s Standards for the Treatment of Historic Properties (often shortened as the Secretary’s Standards). The Secretary’s Standards were developed by the National Park Service to help owners and residents plan sensitive preservation projects.

Depending upon the district and its level of designation (contributor or individually eligible), different restrictions and review processes may apply to newly proposed projects based on locally adopted ordinances and design guidelines. The City of San Mateo’s current Historic Preservation Ordinance requires projects within the Downtown Historic District to adhere to the Secretary’s Standards. The local review process does not currently apply to the contributors of other identified historic districts, and it would not apply to districts that are listed or determined eligible for listing in the California Register or National Register in the future, unless the City’s historic ordinance was amended. However, CEQA review would apply to all projects within any listed or eligible districts (see below).

In the Downtown Historic District, property owners are allowed by right to make minor façade alterations that meet the adopted Downtown Historic District Design Guidelines. Proposals for more substantial alterations to contributors may require the approval of a Site Plan and Architectural Review planning application, as well as review of the project by an independent architectural historian to determine that the proposed scope of work complies with the Secretary’s Standards and the Downtown Historic District Design Guidelines. Infill construction on non-contributing properties may also require analysis by an architectural historian to assess impacts to the surrounding district.

Demolition of a contributor in the Downtown Historic District is not allowed in most cases and would be approved only if the building poses a serious life-safety threat that cannot feasibly be corrected. Such a project would require a Historic Building Demolition Permit to be approved by the City Council, supported by studies documenting the building’s condition, health and safety code deficiencies, and the costs associated with corrective measures.

The California Environmental Quality Act (CEQA) is a state law that establishes a separate review process to assess the impacts of certain types of projects. CEQA covers many areas of the environment, including significant buildings and historic districts (either listed in or eligible for the National Register or California Register). In San Mateo, CEQA review is triggered by projects that require Planning Applications. If one of these projects proposes alterations, demolitions, and new construction in a historic district, the CEQA review process may require an independent architectural historian to analyze the project’s potential impacts to that district. Projects that meet the Secretary’s Standards typically will have a less than significant impact to historic districts and may be exempt from CEQA. More impactful projects may require an environmental document to be prepared, such as an Initial Study or an Environmental Impact Report. Note that CEQA does not necessarily prevent impacts to historic districts, but instead it requires the City and the public to be aware of the impacts to determine whether a project should be approved.

Under CEQA, impacts are usually analyzed to an entire historic district rather than to an individual contributor (unless the contributor itself qualifies as a historic resource). Therefore, substantial alterations or even demolition of a single district contributor that is not individually eligible might not amount to a significant impact if the larger district retains most of its historically or architecturally important qualities.

The National Historic Preservation Act creates its own review process that applies to historic districts listed in or determined eligible for listing in the National Register.

However, this process applies only to projects that receive funding or permits from the federal government, which are not usually initiated by owners of individual properties.

Below is a list of the potential additional items/requirements that could add cost to a contributor to a historic district when they apply for an entitlement or a permit. These additional requirements would apply to additions and exterior alterations, but not to interior remodels.

Design and Permitting Phase

• Submittal of a Planning Application (PA) before a building permit can be submitted may be required as outlined below:
  • Minor facade modifications in the Downtown historic district, which conform to Historic District Design Guidelines, do not require a PA.
  • Additions and facade modifications which may adversely affect the exterior architectural characteristics or historic or aesthetic value of the historic structure, its site or surroundings, require a PA.
  • Determination on if a PA is required is made by the Zoning Administrator based on technical review by a qualified architectural historian.
• Involvement of a qualified architectural historian in the design of the project
  • Preparation of a Secretary of the Interior’s Standards Review by an architectural historian or other documentation may be required depending on the scope of the project and existing documentation on the property.
• Incorporation of specialized products and treatments to meet historic preservation requirements (i.e. custom windows and doors, specialized siding and trim).

Construction Phase

• Involving an architectural historian to inspect and provide input during construction.
  1. Preparation of documentation to confirm adherence to the Secretary of Interior Standards or other historic preservation requirements may be required.
• Using specific construction materials and finishes to meet design specifications and historic requirements.
  1. These type of specialized materials and finishes are often higher cost than standard materials and finishes.
• Retaining and retrofitting of portions of the structure that may otherwise have been allowed to be demolished and rebuilt.

Regarding the Secretary of the Interior’s Standards Review requirement, the City would not require this review for contributors or eligible resources within a designated district where the proposed project at these sites meets Secretary of Interior’s Standards and/or Downtown Historic District Design Guidelines in consultation with the City’s architectural historian. The City also does not require Secretary of the Interior’s Standards Review for sites within the City that were already surveyed. In 1989, if the structures were 50 years old at the time and were determined to not qualify as historic resources. City staff will also discuss with the architectural historian and screen out structures over 50 years old that don’t appear to meet any historic criteria/integrity (such as 60-year old ranch-style construction) that are not within any designated districts.

However, absent these circumstances, the City would require an Secretary of the Interior’s Standards Review at the design and permitting phase, which would add time and expense for an applicant.

Regarding CEQA, for non-contributors within a district, staff would ensure any replacement project would not negatively impact the historic district as part of CEQA, but existing, non-contributing homes could likely be demolished.  For contributors within a district, the scope of CEQA review would be contextual.  While alteration or demolition of a contributor might not impact the significance of a district, such that a CEQA exemption or Negative Declaration (ND) could be used, an ND may require more time and expense for an applicant. The City would also need to evaluate and monitor whether the significance of the district as a whole could be significantly impacted at some point due to the alteration or demolition of contributors.