Saint Clair County

Saint Clair County, Illinois — key demographics

Population size

• Total population (2020 Census): 257,400

Age

• Median age: ~38.5 years
• Under 18: ~22–23%
• 65 and over: ~17%

Gender

• Female: ~51.5–52%
• Male: ~48–48.5%

Racial/ethnic composition

• Race alone (shares sum to ~100; Hispanic overlaps with race):
  • White: ~63%
  • Black or African American: ~34–35%
  • Asian: ~1.5%
  • American Indian/Alaska Native: ~0.3%
  • Native Hawaiian/Other Pacific Islander: ~0.1%
  • Two or more races: ~3–4%
• Hispanic or Latino (of any race): ~5–6%

Households

• Number of households: ~103,000–104,000
• Average household size: ~2.47
• Family households: ~64% of households
• Married-couple families: ~44% of households
• Households with children under 18: ~29–30%
• One-person households: ~29–30%
• Owner-occupied housing rate: ~66%

Insights

• More racially diverse than Illinois overall, driven by a substantially higher Black share.
• Age structure is near state and national norms; household size is slightly below the U.S. average.

Sources: U.S. Census Bureau (2020 Decennial Census; American Community Survey 2018–2022).

St. Clair County, IL email usage snapshot (2025)

• Estimated email users: ~185,000 adults. Basis: ~200k adult residents and ~92% US adult email adoption.
• Age distribution of email users:
  • 18–34: 32% (59k)
  • 35–49: 26% (48k)
  • 50–64: 24% (44k)
  • 65+: 18% (34k) Email is near-universal under 65; slightly lower adoption among 65+ shifts share modestly away from seniors.
• Gender split: ~52% female, ~48% male among email users, mirroring local population and minimal gender gap in email adoption.
• Digital access and trends (ACS-style indicators):
  • Computer access: ~93% of households have a computer/device.
  • Broadband subscription: ~86% of households subscribe to broadband.
  • No home internet: ~14% of households lack an internet subscription.
  • Smartphone-only reliance: ~11% of households primarily use cellular data, indicating mobile-first access for a notable slice of residents.
• Local connectivity context:
  • As part of the St. Louis metro (Belleville–O’Fallon–East St. Louis corridor), service availability is broad and urban-centric, with remaining access gaps concentrated in lower-income and fringe areas. Overall broadband coverage and density support high email penetration.

Summary of mobile phone usage in Saint Clair County, Illinois

Key size and user estimates

• Population and households: Approximately 257,000 residents and about 104,000 households (latest Census estimates).
• Adult mobile phone users: Roughly 190,000 adults use a mobile phone (about 96% of the ~198,000 adults).
• Adult smartphone users: About 170,000–180,000 adults use a smartphone (roughly 85%–90%).
• Household smartphone access: Around 93% of households have at least one smartphone (≈97,000 households).
• Households with a cellular data plan: About 80% (≈83,000 households).
• Mobile-only home internet (cellular data plan but no fixed home broadband): Approximately 19% of households (≈20,000), notably above the Illinois average of roughly 14%.

Demographic breakdown and usage patterns

• Age: Younger adults (18–34) have the highest mobile-only reliance, with roughly 3 in 10 households in this cohort relying on cellular data only; this is several points higher than the statewide share for the same age group.
• Income: Mobile-only reliance is concentrated among households under $35,000 annual income and among renters. Saint Clair County has a larger share of these groups than the state overall, contributing to higher county-level mobile dependence.
• Race/ethnicity: Black households in the county rely on mobile-only internet at higher rates than White households. Because Black residents comprise a larger share of Saint Clair County’s population than the Illinois average, countywide mobile-only reliance is elevated relative to the state.
• Military presence: The Scott Air Force Base catchment (O’Fallon, Shiloh) skews younger and more mobile-centric (higher 5G device adoption, greater use of unlimited plans), while also exhibiting faster device turnover than the state average.
• Sub-county split: Mobile dependence is highest in East St. Louis and parts of older urban cores with lower fixed-broadband adoption, and lowest in O’Fallon/Shiloh and newer subdivisions where fiber is widely available.

Digital infrastructure and coverage

• Carrier coverage: AT&T, Verizon, and T-Mobile provide near-universal 4G LTE across populated areas. 5G coverage is extensive along the I‑64/I‑70/I‑255 corridors and in East St. Louis, Belleville, Fairview Heights, O’Fallon, Shiloh, and around Scott AFB. Mid-band 5G (for higher capacity) is common in these zones; capacity improvements are most noticeable near retail corridors and high-traffic interchanges.
• Capacity and dead zones: River bottoms, bluffs along the Mississippi, and sparsely populated southeast townships (e.g., around Lenzburg/Fayetteville) experience weaker indoor coverage and lower capacity, leading to more frequent mobile congestion than in metro-adjacent areas.
• Fixed broadband interplay: AT&T Fiber is broadly available in O’Fallon/Shiloh and parts of Belleville; Spectrum cable covers most dense areas. Where fiber/cable adoption is strong, mobile is a complement; where fixed options are limited or adoption lags, households substitute with mobile-only plans.
• Public and civic infrastructure: County public safety supports NG911/wireless E911; municipal facilities, libraries, and schools provide Wi‑Fi offload that moderates peak-hour cellular demand in town centers.

How Saint Clair County differs from Illinois overall

• Higher mobile-only home internet reliance by approximately 4–6 percentage points, driven by income mix, housing stock, and demographic composition.
• Slightly lower desktop/laptop ownership and fixed-broadband subscription, which shifts more day-to-day connectivity onto smartphones.
• A pronounced metro-adjacent 5G footprint (due to St. Louis market densification and the Scott AFB node) relative to many downstate counties, with better highway-corridor coverage than the state average but more noticeable capacity constraints in rural pockets.
• Likely higher share of prepaid and unlimited mobile plans (consistent with county income and age profile), which contributes to heavier mobile data usage per line than the Illinois average.

Methodological notes and sources

• Figures synthesize the U.S. Census Bureau’s 2018–2022 American Community Survey (computer and internet subscription indicators), 2023 population estimates, Illinois/state comparative ACS indicators, CDC/NCHS wireless substitution trends (state-level voice-only reliance), FCC broadband/coverage filings, and national smartphone adoption benchmarks (Pew Research) applied to Saint Clair County’s demographic profile. Estimates are rounded for clarity.

Saint Clair County, IL social media snapshot (modeled from the latest Pew Research Center social platform adoption rates applied to local age structure; ACS 2022/2023 population)

Headline user stats

• Population: ~257,000 residents
• Estimated social users (age 13+): ~159,000 people
  • ≈74% of residents age 13+ (≈62% of total population)
• Device: overwhelmingly mobile-first for social activity

Age groups (share who use social media)

• Teens 13–17: ~95%
• Adults 18–29: ~90%+
• Adults 30–49: ~80%+
• Adults 50–64: ~70%
• Adults 65+: ~40% Implication: the county’s active social audience skews toward 18–49, with meaningful but narrower reach 50–64 and selective reach 65+.

Gender breakdown

• County population is ~52% female, ~48% male. Overall social media participation is close to even, with platform skews:
  • Skews female: Pinterest (female users outnumber male users by ~2.5:1), Instagram and Snapchat (moderate female tilt)
  • Roughly balanced: Facebook, YouTube
  • Skews male: Reddit, X (Twitter), LinkedIn (mild to moderate male tilt)

Most‑used platforms in Saint Clair County (modeled share of residents age 13+ who use each platform; rounded)

• YouTube: ~84%
• Facebook: ~65%
• Instagram: ~48%
• TikTok: ~35%
• Pinterest: ~33%
• Snapchat: ~29%
• LinkedIn: ~26%
• X (Twitter): ~22%
• WhatsApp: ~21%
• Reddit: ~22%

Behavioral trends that matter locally

• Daily use intensity
  • Facebook, Instagram, TikTok, Snapchat, and YouTube drive the highest daily check-ins; many users open apps multiple times per day.
• Content formats
  • Short‑form vertical video (Reels/TikTok/Shorts) leads discovery and reach across 13–34; YouTube long‑form remains strong for how‑to, product research, and local news explainer content in 25–54.
  • Facebook Groups and local pages are key for community updates, events, schools, youth sports, and municipal notices; Marketplace is widely used for local buying/selling.
  • Stories, ephemeral content, and DMs are central to youth and young‑adult engagement; direct messaging is a primary response channel for local businesses.
• Commerce and actions
  • Facebook/Instagram drive the broadest paid reach and event RSVPs; YouTube and Instagram support upper‑funnel awareness; TikTok excels for trend-driven promotions to 13–34; Pinterest performs for home, DIY, food, and seasonal shopping with a predominantly female audience; LinkedIn reaches commuting professionals in healthcare, education, public sector, defense, and logistics.
• Timing
  • Engagement is typically highest evenings (after 6 pm, Central) and weekends; lunchtime posts perform consistently on weekdays.
• News and civic use
  • Adults 30+ lean on Facebook and YouTube for local news and public safety updates; under‑30s increasingly encounter local news via TikTok/Instagram creators and YouTube clips.
• Cross‑platform overlap
  • Significant overlap exists between Facebook and Instagram; TikTok users often also use Instagram/YouTube; use multi‑placement creative to reduce frequency fatigue.

Notes on method

• Counts and percentages are modeled by applying Pew Research Center’s 2024 US adult platform adoption rates and 2023 teen platform adoption rates to Saint Clair County’s age structure (U.S. Census Bureau ACS/QuickFacts). Platform shares and daily‑use patterns reflect Pew 2024 (adults) and Pew 2023 (teens).