San Mateo County

San Mateo County, California — key demographics

Source: U.S. Census Bureau, 2019–2023 American Community Survey (5-year) unless noted; population estimate from the Census Bureau’s Population Estimates Program (July 1, 2023).

• Population size:

  • 2023 estimate: ~748,000
  • 2020 Census: 764,442

• Age:

  • Median age: ~40.7 years
  • Under 18: ~20%
  • 65 and over: ~18%

• Gender:

  • Female: ~50.6%
  • Male: ~49.4%

• Racial/ethnic composition (shares of total population):

  • Hispanic or Latino (of any race): ~25–26%
  • White alone, not Hispanic: ~36–37%
  • Asian alone: ~31–32%
  • Black or African American alone: ~2–3%
  • Native Hawaiian and Other Pacific Islander alone: ~1–2%
  • American Indian and Alaska Native alone: ~0.5%
  • Two or more races: ~8–9%
  • Note: Hispanic/Latino is an ethnicity and can overlap with race categories

• Households:

  • Number of households: ~270,000
  • Average household size: ~2.8 persons
  • Family households: ~65–67% of households
  • Owner-occupied housing rate: ~59–61%

Insights: The county is majority–minority with large Asian and Hispanic populations, a median age slightly above the California average, and household sizes above the U.S. average with most households being family households.

San Mateo County, CA email usage (estimates, 2024):

• Estimated users: ≈620,000 residents use email, about 82% penetration among the county’s ≈760,000 population.
• Age distribution of email users: 13–17: ~6%; 18–29: ~18%; 30–49: ~36%; 50–64: ~24%; 65+: ~16% (reflecting near‑universal adoption among adults and slightly lower usage among seniors).
• Gender split: ~51% female, ~49% male, mirroring the county’s adult population.

Digital access and trends:

• Access is very high: ≈97% of households have a computer and ≈94% subscribe to broadband (ACS). Email is deeply embedded in work/school routines, reinforced by high telework rates (~25% of workers primarily work from home).
• Mobile reliance is meaningful but not dominant: about 10–12% of households are effectively smartphone‑only for internet, so mobile email is routine but not a substitute for broadband for most.
• Libraries and civic facilities provide countywide free Wi‑Fi, supporting access for lower‑income and unhoused residents.

Local density/connectivity facts:

• Population density ≈1,700 people per square mile (≈760k residents over ≈448 square miles of land).
• Most residents live along the US‑101/Caltrain corridor, an area with strong fiber/cable availability and robust 4G/5G coverage, supporting high email reliability and responsiveness.

Mobile phone usage in San Mateo County, CA — 2023–2024 snapshot

Headline usage and adoption

• Estimated users: About 600,000 residents in San Mateo County use smartphones in 2024. This estimate aligns adult cellphone ownership near 97% and smartphone ownership near 90% (Pew, 2023) with the county’s ~600k adults plus most teens, and is consistent with the county’s very high smartphone and cellular-plan household penetration.
• Household penetration (ACS 2023, 1-year):
  • Households with a smartphone: ~97% in San Mateo County vs ~95% statewide.
  • Households with a cellular data plan for a smartphone or other mobile device: ~92–93% county vs ~88% California.
  • Households with any broadband subscription (fixed and/or cellular): ~96% county vs ~91% California.
  • Households without any internet subscription: ~4% county vs ~9% California.
  • Smartphone-only households (smartphone present but no desktop/laptop): ~3% county vs ~7% California. Key insight: San Mateo County exhibits near-saturation smartphone and cellular-plan adoption and far fewer disconnected or smartphone-only households than the state average.

Demographic patterns (ACS 2023, 1-year; county vs California)

• Income:
  • Households under $25,000 without internet: ~14% in San Mateo vs ~18% statewide.
  • $25,000–$74,999 without internet: ~6–7% vs ~11% statewide.
  • $75,000+ without internet: ~2% vs ~4% statewide. Interpretation: Affordability gaps persist but are significantly narrower than the state’s, reflecting higher incomes and stronger device/plan uptake.
• Age of householder:
  • 65+ households without internet: ~9–10% county vs ~12% statewide.
  • Under 65 households without internet: ~3% county vs ~7% statewide. Interpretation: Seniors remain the most at-risk group locally, but the gap is smaller than the state average.
• Race/ethnicity of householder:
  • Hispanic/Latino households without internet: ~6% county vs ~9% statewide.
  • Black households without internet: ~5% county vs ~8% statewide.
  • Asian households without internet: ~3% county vs ~6% statewide.
  • White (non-Hispanic) households without internet: ~3–4% county vs ~6% statewide. Interpretation: San Mateo’s digital divide by race/ethnicity is present but attenuated compared with the state overall.
• Device mix:
  • Multi-device households (smartphone plus desktop/laptop/tablet) are the norm in San Mateo; reliance on a smartphone as the only computing device is roughly half the statewide rate. Interpretation: Higher device diversity supports heavier, more varied mobile use (tethering, app-to-desktop workflows, and work-from-anywhere patterns).

Digital infrastructure and performance

• Coverage: 4G LTE from all three national carriers (AT&T, T-Mobile, Verizon) covers essentially all populated areas. 5G coverage is extensive along the US‑101 and I‑280 corridors and dense urban areas (Daly City, South San Francisco, San Mateo, Redwood City, Menlo Park). Coastal and hilly areas (Pacifica, Montara, coastside north/south of Half Moon Bay) have more variable signal due to terrain but are materially better than pre‑2020.
• 5G footprint and capacity:
  • Mid-band 5G (2.5–3.7 GHz) is widely deployed, delivering typical urban downlink speeds in the 100–300 Mbps range, with higher peaks near small cells and C‑Band/mid-band sites.
  • Small-cell densification is evident in downtowns and along major arterials and the Caltrain corridor, improving capacity during peak commute hours and events.
• Resilience and public safety:
  • FirstNet (AT&T) coverage is countywide; agencies leverage 700/800 MHz LMR plus LTE for redundancy. Backup power requirements implemented after PSPS/wildfire seasons have increased macro-site resilience compared with pre‑2019.
• Backhaul and fiber:
  • Robust metro fiber along 101/280 and through business districts supports dense 5G and enterprise mobility. New fiber added during Caltrain electrification and ongoing commercial builds has raised backhaul headroom for additional small cells.
• Reliance on cellular for home internet:
  • A smaller share of households depends solely on cellular for home internet in San Mateo (2–3%) than statewide (6–8%), reflecting high fixed broadband availability and income levels. This reduces congestion risk from fixed‑wireless substitution relative to the state.

How San Mateo County differs from state-level trends

• Higher adoption at every step: more households with smartphones and cellular data plans; fewer households offline; fewer smartphone-only households.
• Less affordability constraint and higher device diversity: low-income, senior, and LEP households still face barriers, but at reduced rates compared with California overall.
• Denser 5G and small-cell buildout: earlier and deeper mid-band 5G deployments than many California counties, with strong commuter-corridor engineering that supports consistently high mobile performance.
• Lower cellular-only home internet use: fixed broadband is more prevalent, so mobile networks carry proportionally more on-the-go traffic and less fixed substitution than the state average.
• Intra-county disparities persist: adoption and performance are highest along the 101 tech corridor; parts of East Palo Alto, Daly City, and the coastside show lower subscription rates and more variable radio conditions than affluent central-county cities.

Bottom line San Mateo County is a high-adoption, high-capacity mobile market: roughly 600,000 smartphone users, ~92–93% of households with cellular data plans, and ~96% with broadband. Compared with California overall, the county features faster 5G rollout, greater device diversity, fewer unconnected households, and less reliance on cellular as the primary home connection, with remaining gaps concentrated among seniors, lower-income households, and in terrain-challenged coastal areas.

San Mateo County, CA social media snapshot (2025)

Overall usage

• Population baseline: ≈740,000 residents (2023 ACS). Adults 18+: ≈585,000; teens 13–17: ≈44,000.
• People using at least one social platform: ≈520,000 residents 13+ (≈70% of total population), composed of ≈480,000 adults and ≈40,000 teens.
• Daily usage: ≈340,000–370,000 residents (about two-thirds of 13+ users) engage daily.

Most-used platforms (share of adults using; local estimates grounded in 2024 U.S. usage with Bay Area adjustments where behavior is consistently higher)

• YouTube: ≈83% (~485k adults). Ubiquitous across ages; primary video/search complement.
• Facebook: ≈68% (~398k). Strong with 35+, community groups, events, Marketplace.
• Instagram: ≈50% (~293k). Core for 18–44; Reels drives discovery for food, local events, SMBs.
• Pinterest: ≈35% (~205k). Planning, home, fashion; skews female.
• LinkedIn: ≈40% (~234k). Above U.S. average (≈30%) given tech/professional density; heavy 25–44 use.
• TikTok: ≈33% (~193k). Strong 13–29; short-form video, local dining/rec.
• Snapchat: ≈30% (~176k). Teens/younger adults; messaging + Stories.
• WhatsApp: ≈35% (~205k). Above U.S. average (≈26%) due to large immigrant and multi-lingual households; family and community groups.
• X (Twitter): ≈22% (~129k). News, transit (Caltrain/SamTrans), emergencies, sports.
• Reddit: ≈23% (~135k). Skews male/tech; career, housing, local threads.
• Nextdoor: ≈30% (~176k). Above U.S. average (≈19%); neighborhoods, public safety, city updates, local referrals.

Age profile (likelihood of using any social platform; local rates mirror national patterns)

• 13–17: ≈90–95% use; heavy on YouTube, TikTok, Snapchat; Instagram primary social identity.
• 18–29: ≈90%; Instagram/TikTok dominant, YouTube universal; WhatsApp/Snapchat for messaging; Facebook relatively low.
• 30–49: ≈82–85%; YouTube, Instagram, Facebook stable; LinkedIn usage high; WhatsApp common for family comms.
• 50–64: ≈70–75%; Facebook and YouTube lead; Nextdoor grows; WhatsApp adoption rising.
• 65+: ≈50–55%; Facebook and YouTube primary; Nextdoor for neighborhood info.

Gender breakdown (overall usage near parity; platform skews)

• Overall: men and women both ≈80%+ use at least one platform.
• Skews: Pinterest (women >> men), Instagram (women > men), Reddit and X (men > women), YouTube near parity, Facebook near parity to slight female tilt.

Behavioral trends in the county

• Video-first consumption: YouTube is the default “second search engine”; Reels/TikTok drive restaurant, hiking, and local attractions discovery.
• Neighborhood-first engagement: Nextdoor and Facebook Groups are central for city alerts, school/PTA, safety, services, and hyperlocal recommendations.
• Professional networking: LinkedIn usage is materially above national norms; active job switching, event networking, and thought leadership are common.
• Messaging ecosystems: WhatsApp is widespread across Hispanic and Asian communities; iMessage group chats are prevalent; community WeChat/Telegram pockets exist for language and tech/crypto circles.
• Local news/transport: X usage concentrates around breaking news, storm/power/PSPS alerts, and Caltrain/BART/SamTrans updates; city/county agencies cross-post to Facebook/Nextdoor.
• Commerce and SMB marketing: Instagram + Facebook lead for local businesses; Marketplace and Nextdoor power P2P selling and service referrals; creators and restaurants lean into short-form video for demand generation.
• Civic participation: High engagement with municipal posts, ballot info, and public meetings, especially during storms, wildfire season, and infrastructure projects.

Notes on methodology

• Population from latest ACS county estimates; platform percentages reflect 2024 Pew Research Center U.S. adult usage rates, with reasonable Bay Area lifts applied to LinkedIn, WhatsApp, and Nextdoor based on consistent regional patterns. Counts are rounded estimates for planning accuracy.