105,776 residents live across 14 ZIPs covering 591 sq mi, served by 14 distinct USPS-recognized cities.
Population moved from 110,377 to 105,776 from 2014 to 2024 — a -4.2% change. 6 ZIPs gained residents, 8 lost.
The county's wealthiest ZIP 60552 (Somonauk, $113,411 median) and poorest ZIP 60115 (Dekalb, $47,043) are 15.8 miles apart — a 2.4× income gap across local geography.
Median home values vary 1.7× across this county — from $188,400 in 60150 (Malta) to $320,500 in 60520 (Hinckley).
Density varies 37× across the county — from 23 people/sq mi in 60550 (Shabbona) to 865 in 60112 (Cortland).
Educational attainment ranges from 19.7% bachelor's+ in 60146 (Kirkland) to 46.8% in 60178 (Sycamore) — the breadth of educational profiles across the area.
Within Illinois, this is the #17 most populous of 102 counties and ranks #12 for median household income .
Weighted by population, the typical household earns about $74,070 across the county — reflecting what a typical resident sees, not a simple ZIP average.
32.8% of adults age 25+ hold a bachelor's degree or higher (21,151 of 64,526 reporting).
14 Standard delivery, 0 PO Box only, 0 single-entity Unique ZIPs serve this county.
| ZIP | City | Type | Population | Median Income | Area (sq mi) | 10-yr Growth |
|---|---|---|---|---|---|---|
| 60115 | Dekalb | Standard | 42,536 | $47,043 | 80.5 | -8.5% |
| 60178 | Sycamore | Standard | 22,224 | $92,913 | 68.4 | 0.8% |
| 60548 | Sandwich | Standard | 11,721 | $82,957 | 41.0 | -3.7% |
| 60135 | Genoa | Standard | 7,274 | $98,033 | 47.9 | 2.4% |
| 60112 | Cortland | Standard | 4,621 | $72,831 | 5.3 | -0.7% |
| 60552 | Somonauk | Standard | 4,285 | $113,411 | 27.2 | -4.0% |
| 60520 | Hinckley | Standard | 2,979 | $98,958 | 44.6 | 5.4% |
| 60145 | Kingston | Standard | 2,464 | $108,477 | 34.1 | -1.7% |
| 60146 | Kirkland | Standard | 2,369 | $88,032 | 53.4 | -15.8% |
| 60556 | Waterman | Standard | 2,138 | $100,186 | 52.0 | 17.8% |
| 60150 | Malta | Standard | 1,738 | $86,719 | 55.1 | 15.2% |
| 60550 | Shabbona | Standard | 941 | $81,574 | 40.5 | -39.1% |
| 60111 | Clare | Standard | 257 | $84,583 | 20.5 | -2.3% |
| 60129 | Esmond | Standard | 229 | $117,750 | 20.7 | 39.6% |