| ZIP Codes: | 17 ZIP Codes (15 Standard, 2 PO Box, 0 Unique) [See All] |
| Area Codes: | 309 / 861 |
| Timezone: | Central (GMT -06:00) |
| Local Time: | 2:12:01 PM |
| Population: | 49,261 [See All] |
| FIPS: | 17095 |
| CBSA: | Galesburg, IL |
| Land Area: | 700 sq mi |
| Water Area: | 3 sq mi |
| Coordinates: | 40.9399, -90.2497 |
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49,261 residents live across 17 ZIPs covering 700 sq mi, served by 16 distinct USPS-recognized cities.
Population moved from 52,666 to 47,638 from 2014 to 2024 — a -9.5% change. 6 ZIPs gained residents, 10 lost.
The county's wealthiest ZIP 61489 (Williamsfield, $98,125 median) and poorest ZIP 61414 (Altona, $48,929) are 15.6 miles apart — a 2.0× income gap across local geography.
Median home values vary 3.7× across this county — from $77,300 in 61458 (Maquon) to $285,100 in 61428 (Dahinda).
Density varies 76× across the county — from 8 people/sq mi in 61458 (Maquon) to 647 in 61439 (Henderson).
Educational attainment ranges from 0.8% bachelor's+ in 61402 (Galesburg) to 33.8% in 61428 (Dahinda) — the breadth of educational profiles across the area.
Within Illinois, this is the #29 most populous of 102 counties and ranks #55 for median household income .
Weighted by population, the typical household earns about $58,828 across the county — reflecting what a typical resident sees, not a simple ZIP average.
21.0% of adults age 25+ hold a bachelor's degree or higher (7,240 of 34,437 reporting).
15 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.
One ZIP holds the majority of this county's population — a sign of a county built around a single city or town.
Knox County lost 6.5% of residents between 2014 and 2024. ZIPs that shed the largest share:
| ZIP | City | Type | Population | Median Income | Area (sq mi) | 10-yr Growth |
|---|---|---|---|---|---|---|
| 61401 | Galesburg | Standard | 30,580 | $50,546 | 120.3 | -12.1% |
| 61448 | Knoxville | Standard | 3,947 | $82,500 | 42.0 | 2.1% |
| 61410 | Abingdon | Standard | 3,838 | $62,925 | 45.2 | 8.6% |
| 61402 | Galesburg | PO Box | 1,623 | — | 0.0 | — |
| 61428 | Dahinda | Standard | 1,278 | $77,143 | 27.7 | 44.6% |
| 61467 | Oneida | Standard | 1,159 | $88,472 | 53.1 | 1.7% |
| 61488 | Wataga | Standard | 1,084 | $68,333 | 22.4 | -8.3% |
| 61489 | Williamsfield | Standard | 820 | $98,125 | 51.6 | -13.7% |
| 61436 | Gilson | Standard | 745 | $76,000 | 63.0 | -23.9% |
| 61572 | Yates City | Standard | 732 | $73,125 | 34.4 | -40.0% |
| 61430 | East Galesburg | Standard | 713 | $79,333 | 1.5 | -11.6% |
| 61414 | Altona | Standard | 696 | $48,929 | 48.8 | -15.2% |
| 61458 | Maquon | Standard | 656 | $65,461 | 77.3 | -34.5% |
| 61472 | Rio | Standard | 453 | $76,500 | 41.9 | -11.2% |
| 61485 | Victoria | Standard | 417 | $59,306 | 44.4 | -28.5% |
| 61439 | Henderson | PO Box | 299 | $59,125 | 0.5 | 34.1% |
| 61474 | Saint Augustine | Standard | 221 | $59,583 | 25.9 | 33.9% |