| ZIP Codes: | 30 ZIP Codes (24 Standard, 6 PO Box, 0 Unique) [See All] |
| Area Codes: | 618 / 730 |
| Timezone: | Central (GMT -06:00) |
| Local Time: | 2:12:03 PM |
| Population: | 247,743 [See All] |
| FIPS: | 17163 |
| CBSA: | St. Louis, MO-IL |
| Land Area: | 664 sq mi |
| Water Area: | 17 sq mi |
| Coordinates: | 38.5235, -89.9936 |
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247,743 residents live across 30 ZIPs covering 664 sq mi, served by 20 distinct USPS-recognized cities.
Population moved from 262,586 to 247,743 from 2014 to 2024 — a -5.7% change. 7 ZIPs gained residents, 20 lost.
The county's wealthiest ZIP 62285 (Smithton, $136,345 median) and poorest ZIP 62201 (East Saint Louis, $27,437) are 18.5 miles apart — a 5.0× income gap across local geography.
Median home values vary 7.0× across this county — from $41,800 in 62205 (East Saint Louis) to $291,800 in 62269 (O Fallon).
Density varies 74× across the county — from 27 people/sq mi in 62255 (Lenzburg) to 2,000 in 62226 (Belleville).
Educational attainment ranges from 10.5% bachelor's+ in 62204 (East Saint Louis) to 52.0% in 62269 (O Fallon) — the breadth of educational profiles across the area.
Within Illinois, this is the #9 most populous of 102 counties and ranks #52 for median household income .
Weighted by population, the typical household earns about $76,235 across the county — reflecting what a typical resident sees, not a simple ZIP average.
31.9% of adults age 25+ hold a bachelor's degree or higher (54,393 of 170,452 reporting).
24 Standard delivery, 6 PO Box only, 0 single-entity Unique ZIPs serve this county.
Median household income spans 5.0× between the wealthiest and poorest ZIPs — a sign of significant intra-county inequality.
Saint Clair County lost 5.7% of residents between 2014 and 2024. ZIPs that shed the largest share:
| ZIP | City | Type | Population | Median Income | Area (sq mi) | 10-yr Growth |
|---|---|---|---|---|---|---|
| 62269 | O Fallon | Standard | 35,923 | $103,818 | 29.6 | 13.0% |
| 62221 | Belleville | Standard | 29,875 | $82,271 | 34.5 | 2.9% |
| 62226 | Belleville | Standard | 28,255 | $70,797 | 14.1 | -4.6% |
| 62220 | Belleville | Standard | 19,152 | $65,952 | 29.3 | -4.6% |
| 62208 | Fairview Heights | Standard | 16,821 | $80,205 | 13.6 | -0.9% |
| 62223 | Belleville | Standard | 16,269 | $73,700 | 25.4 | -6.2% |
| 62206 | East Saint Louis | Standard | 12,959 | $33,838 | 14.7 | -20.1% |
| 62258 | Mascoutah | Standard | 10,437 | $94,655 | 77.7 | 10.5% |
| 62232 | Caseyville | Standard | 7,063 | $64,269 | 13.0 | -1.3% |
| 62207 | East Saint Louis | Standard | 6,984 | $29,845 | 6.5 | -17.3% |
| 62254 | Lebanon | Standard | 6,710 | $96,492 | 42.2 | 17.9% |
| 62260 | Millstadt | Standard | 6,668 | $91,039 | 45.5 | -1.7% |
| 62205 | East Saint Louis | Standard | 6,459 | $45,672 | 5.9 | -25.3% |
| 62243 | Freeburg | Standard | 6,418 | $103,342 | 54.1 | 8.5% |
| 62203 | East Saint Louis | Standard | 5,465 | $42,111 | 6.3 | -23.7% |
| 62225 | Scott Air Force Base | Standard | 5,242 | $103,284 | 5.3 | -1.9% |
| 62201 | East Saint Louis | Standard | 4,921 | $27,437 | 16.5 | -37.7% |
| 62285 | Smithton | Standard | 4,239 | $136,345 | 16.0 | -3.0% |
| 62239 | Dupo | Standard | 4,232 | $61,191 | 8.7 | -13.5% |
| 62204 | East Saint Louis | Standard | 4,055 | $35,346 | 5.4 | -52.9% |
| 62264 | New Athens | Standard | 3,097 | $57,015 | 70.7 | -4.4% |
| 62257 | Marissa | Standard | 2,046 | $78,750 | 69.0 | -34.8% |
| 62240 | East Carondelet | Standard | 1,796 | $96,063 | 15.9 | -19.5% |
| 62255 | Lenzburg | Standard | 1,092 | $80,506 | 40.6 | 23.1% |
| 62059 | Lovejoy | PO Box | 729 | $30,673 | 0.8 | -9.7% |
| 62282 | Saint Libory | PO Box | 563 | $117,143 | 1.0 | 14.0% |
| 62289 | Summerfield | PO Box | 273 | $47,237 | 0.8 | -29.3% |
| 62222 | Belleville | PO Box | — | — | 0.0 | — |
| 62071 | National Stock Yards | PO Box | — | — | 0.3 | — |
| 62202 | East Saint Louis | PO Box | — | — | 0.0 | — |