Zip Code 51040 — Onawa, IA
51040 is a ZIP Code associated with Onawa, IA, located within Monona. 51040 ranks #1 out of 9 ZIP codes in Monona County by population (and #178 out of 970 in IA). The area supports an estimated population of 3,500 residents across Data Pending housing units, with a population density of 10.4 people per square mile.
WorldPlaceData database updated: October 2026
📍 View location on OpenStreetMap (42.030730, -96.070600)
| Data Metric | Local Statistic |
|---|
| Postal / Zip Code | 51040 |
| Primary City | Onawa |
| State / Province | IA |
| County | Monona |
| Total Population | 3,500 |
| Median Household Income | Data Pending |
| Total Housing Units | Data Pending |
| Population Density | 10.4 people/sq mi |
| Timezone | America/Chicago |
How 51040 Compares
| Metric | ZIP 51040 | Monona County | IA State Average |
|---|
| Population | 3,500 | 8,715 (Total) | 3,210,984 (Total) |
| Average ZIP Income | Data Pending | N/A | N/A |
| Population Density | 10.4 /sq mi | -- | -- |
| County Pop Rank | #1 of 9 | -- | -- |
Nearby ZIP Codes
Data Sources & Methodology: Geographic coordinates and ZIP Code assignments are derived from underlying geographic and postal datasets. Note that ZIP Codes are USPS postal delivery areas, while Census ZCTAs are statistical approximation areas. Read full methodology →