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California · San Francisco Peninsula · Bay Area · #93 Most Populous County in the US
San Mateo County, California
The San Francisco Peninsula - between the Bay and the Pacific, connecting San Francisco to Silicon Valley. Property tax, courts, public records, probate, and senior services for San Mateo County residents.
Affiliate disclosure: This page contains affiliate links. We may earn a commission if you use them, at no extra cost to you. Our editorial recommendations are independent of these relationships.
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San Mateo County's assessment ratio means effective tax rates are low — but incorrect appraisals still cost money. Ownwell manages the appeal with no upfront cost.
Shelter Info: Multiple shelter locations; contact OES; San Mateo County Fairgrounds; Red Cross
FEMA Region: Region 9
Notes: San Francisco Peninsula county; Redwood City is county seat; earthquake risk (San Andreas Fault runs through the peninsula – Crystal Springs Reservoir fills a rift valley on the fault; 1906 San Francisco earthquake began on this segment of the fault); landslide risk (Santa Cruz Mountains slopes on the ocean side – 1982 and 1998 storms caused major landslides); tsunami risk (Pacific coast); wildfire risk (Santa Cruz Mountains – 2020 CZU Lightning Complex Fire burned significantly in adjacent Santa Cruz County but threatened San Mateo); sea level rise (extensive Bay shoreline); SFO flood risk
Roads & Utilities
ROADS & TRANSPORTATION
County Roads: San Mateo County Public Works – (650) 363-4100
Transit: SamTrans – (800) 660-4287 | samtrans.com; Caltrain (commuter rail between San Francisco and San Jose – heavy use by tech workers; Peninsula’s lifeline transit); BART (extends through Millbrae and SFO into San Mateo County); SFO AirTrain; ferry services (San Francisco Bay Ferry); Amtrak Coast Starlight (San Jose connection)
Airport: San Francisco International Airport (SFO – on the Bay in San Mateo County; the airport is in unincorporated San Mateo County near South San Francisco and Millbrae; one of the world’s busiest airports)
Notes: US-101 runs north-south through the Bay side; I-280 (one of California’s most scenic freeways – runs through the Crystal Springs watershed in the coastal hills; often called the most beautiful freeway in the US by car enthusiasts); SR-92 and SR-35 (Skyline Blvd – runs along the ridge of the Santa Cruz Mountains from Daly City to Santa Cruz County); Caltrain’s Baby Bullet express service connects SF to San Jose in under an hour; tech company shuttles from Caltrain stations to Silicon Valley campuses are iconic; the county’s tech workforce drives extreme commuting pressures
Business & Permits
BUILDING & PERMITS
Office: San Mateo County Planning and Building – (650) 363-4161 | smcgov.org/planning
Services: County permits; 20 cities (Redwood City, Daly City, South San Francisco, San Mateo, Burlingame, San Bruno, Pacifica, Belmont, Foster City, Menlo Park, East Palo Alto, Millbrae, San Carlos, Half Moon Bay, Atherton, Portola Valley, Woodside, Hillsborough, Brisbane, Colma – city of the dead; 17 cemeteries and 1,500 residents) have separate permits
Notes: San Mateo County has extremely active building driven by the tech industry; office parks along US-101 (the “Billion Dollar Mile” was originally the term for the tech companies along US-101 in San Mateo County); transit-oriented development near Caltrain stations; Half Moon Bay and coastal communities have strict Coastal Act development controls; Atherton, Hillsborough, and Woodside are among the wealthiest zip codes in the US and have very restrictive development rules; SFO expansion requires complex county coordination
Veterans Services
VETERANS SERVICES
Office: San Mateo County Human Services Agency Veterans Services – (650) 802-7500
VA Medical: VA Palo Alto Health Care System – (650) 493-5000 (accessible from San Mateo County via US-101); VA San Francisco accessible; multiple CBOCs
Services: Benefits claims, VA healthcare enrollment; CalVet coordination
Notes: VA Palo Alto is an excellent and accessible facility; San Mateo County has a significant veteran population (tech industry includes many veteran entrepreneurs and employees); CalVet coordination; Stanford University’s Continuing Studies veteran student programs
Libraries
LIBRARIES
System: San Mateo County Libraries – (650) 312-5348 | smcl.org; 12 branches in unincorporated areas and smaller cities; Redwood City Public Library (separate); Daly City Library (separate); San Mateo Public Library (separate); South San Francisco Library; Pacifica; Burlingame; multiple city systems
Services: Books, e-books, public computers, Wi-Fi, genealogy, tech industry collections, maker spaces, children’s programs; multilingual in Spanish, Chinese, Tagalog, and others; Credo Reference academic database access
Notes: San Mateo County Libraries is an excellent library system; the tech industry’s presence is reflected in maker space equipment (laser cutters, 3D printers, recording studios); the county’s diverse communities (significant Chinese-American community in Daly City, Filipino-American communities in Daly City and South San Francisco, Hispanic community in Redwood City/East Palo Alto) drive excellent multilingual services; the extraordinary wealth of some communities (Atherton has the highest median household income of any US city) creates exceptional library funding
Parks & Recreation
PARKS & RECREATION
County Parks: San Mateo County Parks – (650) 363-4020 | parks.smcgov.org; 18,000+ acres of parks and open space; Huddart Park; Pescadero Creek County Park; Crystal Springs Regional Trail; Sam McDonald Park; Wunderlich Park; Edgewood County Park (wildflower meadows – California’s finest display of non-desert wildflowers in spring)
State Parks: San Mateo County Memorial Park; Half Moon Bay State Beach (the O’Neill Beach; popular Bay Area getaway); Año Nuevo State Park (Pigeon Point area – the largest mainland elephant seal breeding colony in the US; thousands of elephant seals congregate for breeding in December-March; reserve tours required; one of California’s most extraordinary wildlife experiences)
Open Space: Midpeninsula Regional Open Space District (MROSD) – (650) 691-1200 | openspace.org (manages 70,000+ acres of open space in the Santa Cruz Mountains and coastal hills; Skyline Ridge Open Space Preserve; Russian Ridge; Monte Bello – spectacular views to the Bay and the Pacific; protects the watershed and provides extraordinary hiking close to millions of people)
Notable: SFO (airport itself is a significant facility within the county); Crystal Springs Reservoir (the San Andreas Fault rift valley holding the SF water supply; beautiful from I-280; watershed closed to the public to protect SF’s drinking water – one of the most carefully protected urban watersheds in the US; the SFPUC’s Crystal Springs watershed protects a remarkably wild natural area in the middle of one of the most densely developed regions in the US); Filoli (Woodside – National Trust Historic Site; a magnificent 1917 country estate with stunning gardens; used as the exterior of the Carrington family mansion in “Dynasty”; one of the most beautiful historic estates in California)
Notes: Año Nuevo State Park’s elephant seal colony is one of California’s most extraordinary wildlife experiences – thousands of massive elephant seals (males weigh up to 2,500 lbs) engage in dramatic mating battles while pups are born; reserve tours are required but the experience is unforgettable; Edgewood County Park’s spring wildflower meadows (dozens of species including rare manzanita and calypso orchid) are exceptional; MROSD’s open space network makes the Peninsula one of the best-served urban counties for hiking and natural open space in the US; Filoli’s gardens are simply extraordinary; the Crystal Springs watershed’s dramatic beauty from I-280 (the reservoir fills the San Andreas Fault rift valley – you are literally driving along one of the world’s most significant active faults) is one of California’s most dramatic freeway experiences
GIS & Maps
GIS & MAPS
GIS Portal: San Mateo County GIS – smcgov.org/gis | (650) 363-4100; MROSD GIS; SFPUC Crystal Springs watershed maps; USGS San Andreas Fault maps; SFO development maps; sea level rise inundation maps
Notes: Sophisticated GIS; San Andreas Fault mapping through Crystal Springs Reservoir is critical; MROSD open space mapping; SFO expansion and sea level rise mapping; Bay shoreline restoration maps; Foster City sea level rise risk mapping (Foster City is on fill adjacent to the Bay and faces significant sea level rise risk)
Animal Services
ANIMAL SERVICES
Shelter: San Mateo County Animal Services – (650) 340-7022; Peninsula Humane Society & SPCA (PHS/SPCA – the primary animal welfare organization for San Mateo County and San Francisco; (650) 340-7022 | peninsulahumane.org)
Notes: Peninsula Humane Society & SPCA is one of the Bay Area’s finest animal welfare organizations; excellent adoption programs; SFO wildlife management (bird strikes – the Bay and marshes adjacent to SFO attract enormous bird populations; USDA Wildlife Services manages bird hazards for SFO); elephant seal management at Año Nuevo by State Parks and docents; Coyote management; mountain lion management in the Santa Cruz Mountains (Santa Cruz Mountains lion population is genetically distinct from other California populations)
Environmental & Waste
ENVIRONMENTAL / WASTE MANAGEMENT
Solid Waste: San Mateo County RecycleWorks – (650) 637-3473 | recycleworks.org; city collection programs; excellent regional coordination; Shoreway Environmental Center (San Carlos – materials recovery and composting facility)
Recycling: Outstanding programs – San Mateo County has some of the highest diversion rates in California; zero waste programs; organics composting; hazardous waste programs; e-waste recycling
Environmental: California Coastal Commission; SF Bay RWQCB; SFPUC (Crystal Springs watershed – protecting SF’s drinking water supply); MROSD (watershed protection in the Santa Cruz Mountains); Caltrans I-280 noise and stormwater; Baylands restoration along the Bay shoreline; Foster City and other Bay-edge development sea level rise
Notes: The Crystal Springs watershed (protected by SFPUC as the primary storage for SF’s Hetch Hetchy water supply) is one of the most intact natural areas on the San Francisco Peninsula – its protection has prevented development that would otherwise have occurred over 150 years; the San Andreas Fault runs directly through the watershed; the SFPUC’s watershed stewardship has preserved a remarkable remnant of the original peninsula landscape; sea level rise is a critical long-term challenge for Bay-adjacent communities – Foster City (built on Bay fill), the Coyote Point area, and SFO itself face significant inundation risk by 2050-2100; Bay restoration (the South Bay Salt Pond Restoration Project – the largest tidal wetland restoration project in the western US) is actively restoring former industrial salt ponds to tidal marsh, which also provides sea level rise buffering; the Santa Cruz Mountains face increasing wildfire risk and MROSD is implementing prescribed burn programs; the county’s wealth and strong environmental consciousness drive exceptional environmental management relative to most California counties
About San Mateo County
San Mateo County occupies the northern two-thirds of the San Francisco Peninsula – the long, narrow strip of land between San Francisco Bay and the Pacific Ocean, extending south from the city of San Francisco to Silicon Valley. The county seat is Redwood City; other major communities include San Mateo, Burlingame, Daly City (San Mateo County’s largest city by population), South San Francisco, Foster City, San Bruno, Millbrae, Half Moon Bay, Menlo Park, and Palo Alto-adjacent East Palo Alto. The county contains San Francisco International Airport (SFO) within its borders, making it a major employment and transit hub for the entire Bay Area.
San Mateo County is one of the wealthiest counties in the United States – consistently ranking among the top 5 counties nationally by median household income. The county’s affluence reflects its position between two of the world’s most concentrated technology clusters: San Francisco to the north and Silicon Valley (Santa Clara County) to the south. Major employers include Oracle, Gap Inc., Salesforce (some offices), biotech firms in South San Francisco’s “Biotech Bay,” and SFO-related industries. County government is a five-member Board of Supervisors with a County Manager, and separately elected offices for the Assessor-County Clerk-Recorder & Elections (ACRE), District Attorney, Sheriff, and Controller.
All Services
Browse every category and topic available for this county.
California property tax is governed by Proposition 13 (1978): the base rate is 1% of assessed value, with a maximum 2% annual increase. Assessed value is the purchase price (base year value) – in San Mateo County, where median home values have surged past $1 million in most communities, long-term Prop 13 owners often pay taxes on assessed values a fraction of current market value.
The San Mateo County Assessor-County Clerk-Recorder & Elections (ACRE) at 555 County Center, First Floor, Redwood City (650-599-1227) administers property assessment.
Two pathways to challenge your assessment:
Informal – Decline in Value (Prop 8) Program: If your property’s current market value has fallen below its Prop 13 assessed value, apply to the Assessor’s informal Decline in Value program through smcacre.gov. The informal enrollment deadline is October 31 annually. If enrolled and you disagree with the Assessor’s decision, file a formal AAB appeal before the November 30 deadline.
Formal – Assessment Appeals Board (AAB): The filing deadline for regular assessment appeals is July 2 through November 30 each year (for 2025 the deadline rolled to Monday December 1 due to the November 30 Sunday). File online via smcgov.org/ceo/assessment-appeals-board or email [email protected]. The AAB Clerk is at 500 County Center, 5th Floor, Redwood City (650-363-4573). Hearings are held in-person only (since May 1, 2025) in the Board of Supervisors’ Chambers, 500 County Center, 1st Floor, Redwood City.
Hearing preparation: Bring 8 copies of all documentary evidence to the hearing. You must be present during roll call. The AAB can lower, maintain, or raise your assessed value. You must continue paying taxes during the appeal; refunds are issued with interest if a reduction is granted. Supplemental and escape assessment appeals must be filed within 60 days of the notice date.
San Mateo County’s Prop 13 effective rate including local voter-approved additions typically runs 1.1–1.3% depending on location and applicable special districts. Tax bills are due November 1 and February 1, delinquent after December 10 and April 10. Prop 19: Parent-to-child transfers of primary residences no longer automatically preserve the base year value; the child must occupy it as a primary residence, and the exclusion is capped at $1 million above the assessed value. Critical planning issue in San Mateo County given extreme values.
California has no state estate tax and no inheritance tax.
OWNWELL CTA: San Mateo County AAB approves roughly 60% of properly filed appeals. Formal deadline July 2–November 30 (December 1 when Nov 30 is a Sunday). Informal decline-in-value enrollment by October 31. Prop 19 family transfer changes are especially significant in this market. Ownwell manages the appeal with no upfront cost.
Recommended
San Mateo County AAB approves roughly 60% of properly filed appeals. Formal deadline July 2–November 30 (December 1 when Nov 30 is a Sunday). Informal decline-in-value enrollment by October 31. Prop 19 family transfer changes are especially significant in this market. Ownwell manages the appeal with no upfront cost.
Courts & Legal
Courts & Legal
The San Mateo County Superior Court at 400 County Center, Redwood City (650-261-5100) handles all civil, criminal, family, and probate matters. The San Mateo County Assessor-County Clerk-Recorder & Elections (ACRE) at 555 County Center maintains all land records – deeds, mortgages, and recorded documents. Records are searchable at smcacre.gov.
California probate is governed by the California Probate Code. California has no state estate tax and no inheritance tax. Prop 19 is the defining estate planning issue for San Mateo County homeowners – with properties valued at $1–5 million or more, the loss of the broad parent-child base year value transfer under old law (replaced by the capped Prop 19 exclusion) has major tax consequences for heirs.
Senior Services: The San Mateo County Aging and Adult Services (650-573-3900) and the C/CAG (City/County Association of Governments) Human Services Agency coordinate senior programming, home-delivered meals, transportation, HICAP Medicare counseling, caregiver support, and connections to Medi-Cal long-term care programs. The IHSS (In-Home Supportive Services) program provides Medi-Cal-funded in-home care for qualifying seniors and disabled residents.
Prop 19 base year transfer for seniors: Qualifying homeowners 55 or older may transfer their Prop 13 base year value to a replacement home anywhere in California, up to three times. In San Mateo County – where seniors may have a $200,000 assessed value on a home worth $2 million – this benefit is particularly powerful for those considering downsizing anywhere in California.
Marriage & Vital Records
Marriage licenses, divorce records, and birth & death certificates are handled by the following office(s):
CLERK-RECORDER (Deeds, Marriage Licenses)
555 County Center, 1st Floor, Redwood City, CA 94063
(650) 363-4500
County Clerk
(650) 312-5222
Genealogy
County-level record sources
San Mateo County Superior Court (marriage licenses, will and estate case files – see Probate section above)
Local societies
San Mateo County Genealogical Society, San Mateo County, CA – holds birth, deed, and other historical records for the county.
Probate & Estate
Losing someone and having to deal with courts and paperwork at the same time is hard. This section won’t make that easier, but it should tell you what to expect, what it costs, and where to go – so at least you’re not walking in blind.
Where to go
San Mateo County Superior Court – Hall of Justice 400 County Center, Redwood City, CA 94063 (650) 261-5100 Hours: Monday–Friday, 8:00 a.m.–4:00 p.m.
Step 1: figure out which path applies
California recently increased its small-estate thresholds substantially, so check this first – more estates now qualify to skip full probate than in past years.
Small Estate Affidavit (personal property) – for estates with personal property valued at $208,850 or less (for deaths on or after April 1, 2025; holds through March 31, 2028). No court filing needed – present the signed affidavit directly to the bank or institution holding the property. Must wait at least 40 days after the death, and no probate proceeding can already be pending.
Petition to Determine Succession to Real Property, Primary Residence – for a decedent’s primary California residence valued at $750,000 or less (Judicial Council Form DE-310) – with Bay Area property values, many San Mateo County families will fall well above the old threshold but still under this newer, higher one. Requires a 40-day wait, notice to heirs, and a probate referee appraisal.
Affidavit for Real Property of Small Value – for other (non-primary-residence) California real property valued at $69,625 or less (Form DE-305). Requires a 6-month wait.
Formal Probate – required when the estate exceeds these thresholds. California typically uses the Independent Administration of Estates Act (IAEA), letting the personal representative handle most matters without a court hearing for each step.
California is a community property state – a surviving spouse already owns their half of community property, and can often use a simplified Spousal Property Petition (Form DE-221) instead.
If using the small estate affidavit (personal property)
Wait at least 40 days after the death.
Confirm total qualifying California personal property (excluding trust assets, joint tenancy, POD/TOD accounts, and beneficiary-designated accounts) is $208,850 or less, using date-of-death values.
Complete the affidavit under Probate Code § 13100.
Present it with a certified death certificate directly to the bank or institution – no court filing required. Collecting property this way makes you personally liable for the decedent’s unsecured debts up to the value received (Prob. Code § 13109).
IF USING THE PRIMARY RESIDENCE PETITION OR SMALL REAL PROPERTY AFFIDAVIT
Confirm the property qualifies and the applicable waiting period has passed (40 days for the primary-residence petition; 6 months for the small real property affidavit).
File the petition (Form DE-310) or affidavit (Form DE-305) with the San Mateo County Superior Court.
A probate referee appraises the property; heirs receive notice.
Once approved, the property transfers without full probate administration.
If formal probate is required
Deliver the original will (if any) to the court clerk within 30 days of learning of the death (Prob. Code § 8200).
File a Petition for Probate (Form DE-111) to admit the will and request appointment as personal representative.
The court issues Letters Testamentary (Form DE-150) or Letters of Administration.
If Independent Administration authority is granted, the personal representative can act on most matters without separate court hearings.
Notice to creditors and an inventory/appraisal (with a probate referee) follow, along with payment of debts and taxes.
The estate closes with a final petition for distribution.
What it costs
Small estate affidavit / real property affidavits: no court filing fee for the personal-property affidavit; filing fees apply to the DE-310 primary-residence petition and DE-305 small real property affidavit.
Formal probate filing fee: several hundred dollars, varying somewhat by county.
Personal representative and attorney compensation: statutory fee schedule based on estate size (Prob. Code §§ 10800–10810) – a percentage that declines as the estate grows.
No California state estate tax or inheritance tax.
Probate filings, estate administration, and guardianship matters are handled by the following office(s):
Public Safety & Arrests
Arrest records, inmate search, and law enforcement services are handled by the following office(s):
SHERIFF
400 County Center, 3rd Floor, Redwood City, CA 94063
(650) 363-4911
Elections & Voting
Voter registration, polling locations, and elections information are handled by the following office(s):
CA Voter Registration
Health & Human Services
Offices & Contacts
Health services, social services, and assistance programs are handled by the following office(s):
Health Dept
(650) 573-2920
Social Services
(650) 802-7400
Medi-Cal
(800) 300-1506
Public Health Information
PUBLIC HEALTH
Office: San Mateo County Health – (650) 573-2346 | smchealth.org
Services: Comprehensive county health department; immunizations; WIC; STI/HIV; behavioral health; environmental health; restaurant inspections; epidemiology
Hospital: San Mateo Medical Center (county public hospital); Stanford Health Care (multiple – Redwood City campus is Stanford’s primary acute care site for the Peninsula; Stanford is one of the world’s top academic medical centers); Sequoia Hospital (Dignity Health – Redwood City); Kaiser Permanente Redwood City; Peninsula Medical Center; Mills-Peninsula Health Services (Burlingame – Sutter Health)
Notes: San Mateo County has exceptional healthcare – Stanford Health Care on the Peninsula is world-class; San Mateo Medical Center is the county’s safety-net hospital; behavioral health demand is significant; East Palo Alto, a lower-income enclave surrounded by wealth, has persistent health disparities; the county’s wealth overall supports strong health outcomes but inequality is significant; SFO’s air quality impacts (jet exhaust, ground vehicle emissions) affect nearby communities
Editorial independence: CountyOffices maintains strict editorial independence from our affiliate partners. Our content is researched from official government sources. Affiliate relationships do not influence our recommendations or the information we publish.
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