| ZIP Codes: | 7 ZIP Codes (6 Standard, 1 PO Box, 0 Unique) [See All] |
| Area Code: | 712 |
| Timezone: | Central (GMT -06:00) |
| Local Time: | 2:11:52 PM |
| Population: | 18,008 [See All] |
| FIPS: | 19059 |
| CBSA: | Spirit Lake, IA |
| Land Area: | 388 sq mi |
| Water Area: | 23 sq mi |
| Coordinates: | 43.3748, -95.1173 |
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18,008 residents live across 7 ZIPs covering 388 sq mi, served by 7 distinct USPS-recognized cities.
Population moved from 17,032 to 18,008 from 2014 to 2024 — a +5.7% change. 5 ZIPs gained residents, 2 lost.
The county's wealthiest ZIP 51331 (Arnolds Park, $89,167 median) and poorest ZIP 51364 (Terril, $66,875) are 9.5 miles apart — a 1.3× income gap across local geography.
Median home values vary 5.4× across this county — from $82,900 in 51363 (Superior) to $448,800 in 51331 (Arnolds Park).
Density varies 30× across the county — from 12 people/sq mi in 51364 (Terril) to 356 in 51331 (Arnolds Park).
Educational attainment ranges from 16.7% bachelor's+ in 51347 (Lake Park) to 44.7% in 51355 (Okoboji) — the breadth of educational profiles across the area.
Within Iowa, this is the #38 most populous of 99 counties and ranks #36 for median household income with the #9 fastest decade growth .
Weighted by population, the typical household earns about $75,948 across the county — reflecting what a typical resident sees, not a simple ZIP average.
31.1% of adults age 25+ hold a bachelor's degree or higher (4,211 of 13,520 reporting).
6 Standard delivery, 1 PO Box only, 0 single-entity Unique ZIPs serve this county.
| ZIP | City | Type | Population | Median Income | Area (sq mi) | 10-yr Growth |
|---|---|---|---|---|---|---|
| 51360 | Spirit Lake | Standard | 8,653 | $75,882 | 119.0 | 3.4% |
| 51351 | Milford | Standard | 4,988 | $73,824 | 109.8 | 11.6% |
| 51347 | Lake Park | Standard | 1,470 | $82,750 | 84.6 | 10.0% |
| 51355 | Okoboji | Standard | 1,048 | $72,262 | 4.4 | 12.8% |
| 51331 | Arnolds Park | Standard | 935 | $89,167 | 2.6 | -15.8% |
| 51364 | Terril | Standard | 803 | $66,875 | 67.0 | 20.2% |
| 51363 | Superior | PO Box | 111 | $75,625 | 0.4 | -28.4% |