| ZIP Codes: | 12 ZIP Codes (10 Standard, 2 PO Box, 0 Unique) [See All] |
| Area Codes: | 309 / 861 |
| Timezone: | Central (GMT -06:00) |
| Local Time: | 2:12:02 PM |
| Population: | 15,633 [See All] |
| FIPS: | 17131 |
| CBSA: | Davenport-Moline-Rock Island, IA-IL |
| Land Area: | 617 sq mi |
| Water Area: | 8 sq mi |
| Coordinates: | 41.1946, -90.6873 |
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15,633 residents live across 12 ZIPs covering 617 sq mi, served by 12 distinct USPS-recognized cities.
Population moved from 16,653 to 15,633 from 2014 to 2024 — a -6.1% change. 2 ZIPs gained residents, 10 lost.
The county's wealthiest ZIP 61281 (Sherrard, $102,639 median) and poorest ZIP 61260 (Joy, $41,645) are 18.9 miles apart — a 2.5× income gap across local geography.
Median home values vary 3.3× across this county — from $67,200 in 61442 (Keithsburg) to $224,000 in 61281 (Sherrard).
Density varies 138× across the county — from 12 people/sq mi in 61476 (Seaton) to 1,608 in 61263 (Matherville).
Educational attainment ranges from 2.7% bachelor's+ in 61442 (Keithsburg) to 32.9% in 61476 (Seaton) — the breadth of educational profiles across the area.
Within Illinois, this is the #68 most populous of 102 counties and ranks #48 for median household income .
Weighted by population, the typical household earns about $75,350 across the county — reflecting what a typical resident sees, not a simple ZIP average.
21.3% of adults age 25+ hold a bachelor's degree or higher (2,388 of 11,212 reporting).
10 Standard delivery, 2 PO Box only, 0 single-entity Unique ZIPs serve this county.
A frontier county — vast land area with only a few residents per square mile. Daily life looks very different here than in the country's denser counties.
Mercer County lost 6.1% of residents between 2014 and 2024. ZIPs that shed the largest share:
| ZIP | City | Type | Population | Median Income | Area (sq mi) | 10-yr Growth |
|---|---|---|---|---|---|---|
| 61231 | Aledo | Standard | 4,962 | $70,991 | 157.7 | -3.5% |
| 61281 | Sherrard | Standard | 2,520 | $102,639 | 40.4 | -5.7% |
| 61272 | New Boston | Standard | 1,437 | $64,167 | 94.0 | -1.2% |
| 61412 | Alexis | Standard | 1,392 | $82,143 | 81.0 | 8.8% |
| 61486 | Viola | Standard | 1,330 | $78,889 | 42.3 | -14.4% |
| 61465 | New Windsor | Standard | 1,192 | $56,875 | 46.8 | -4.1% |
| 61260 | Joy | Standard | 737 | $41,645 | 56.6 | -9.6% |
| 61263 | Matherville | PO Box | 657 | $86,500 | 0.4 | -5.5% |
| 61476 | Seaton | Standard | 551 | $88,264 | 47.1 | -20.3% |
| 61442 | Keithsburg | Standard | 504 | $48,750 | 29.9 | -24.8% |
| 61466 | North Henderson | Standard | 263 | $73,462 | 19.5 | -24.4% |
| 61276 | Preemption | PO Box | 88 | $87,750 | 0.7 | 1.1% |