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Where 51040 is
Approximate ZIP boundary (Census ZCTA 2020). ZIP codes are mail routes, not areas, so the shape shown is the Census tabulation area that approximates it.
- 🔢 Type 51040 into a pocket calculator and turn it upside down: OhOIS — not quite a word, sorry.
- ➕ As a number, 51,040 = 2 × 2 × 2 × 2 × 2 × 5 × 11 × 29. Its digits add up to 10, a total 513 other ZIP codes share.
- 💾In binary, the way a computer stores it:
1100011101100000 - 🏠 Its numerical neighbours: 51039 (Moville, IA, 29 mi away) and 51041 (Orange City, IA, 69 mi away).
- 🔄 Backwards, 51040 becomes 04015 — and that is a real ZIP code: Casco, ME, 1,293 miles away.
- 👥 27 other ZIP codes are made of exactly the same digits (01054, 01450, 01504, 01540, 04015, 04051, …). The farthest-flung twin is 04105 in Falmouth, ME, 1,306 miles away.
- 🧭 Farther north than 75% of all ZIP codes, and farther west than 71%.
- 🎯201 miles northeast of the geographic center of the Lower 48, near Lebanon, Kansas.
- 🌏 Dig straight through the Earth from 51040 and you would come out at 42.03°S, 83.93°E — 831 miles from Port-aux-Français, French Southern Territories, the nearest big city to that spot.
- ☀Longest day of the year: 15h 15m of daylight. Shortest: 9h 07m.
- 📏 At 129.5 square miles of land, 51040 is bigger than 84% of ZIP codes — room for about 98 Central Parks.
- Working out the sun…
- Checking the USGS…
Source: USGS.
People and housing
| Population | 3,500This ZIP3,500 |
|---|---|
| Households | 1,555This ZIP1,555 |
| Housing units | 1,731This ZIP1,731 |
| Median age | 37.6This ZIP37.6Iowa38.6US 38.9 |
| Median household income | $71,179This ZIP$71,179Iowa$75,059US $80,734 |
| Median home value | $151,600This ZIP$151,600Iowa$208,000US $332,700 |
| Median gross rent | $947This ZIP$947Iowa$972US $1,413 |
| Bachelor's degree or higher | 19.9%This ZIP19.9% |
| Mean commute | 18.3 minThis ZIP18.3 min |
| Population density | 27.0 / sq miThis ZIP27.0 / sq mi |
Business and tax activity
| Business establishments | 115This ZIP115 |
|---|---|
| Employees | 1,156This ZIP1,156 |
| Annual payroll | $50,687,000This ZIP$50,687,000 |
| Tax returns filed | 1,500This ZIP1,500 |
| Total adjusted gross income | $105,679,000This ZIP$105,679,000 |
Land area
| Land area | 129.51 sq miThis ZIP129.51 sq mi |
|---|---|
| Water area | 1.61 sq miThis ZIP1.61 sq mi |
Other place names in 51040
Census places whose land this ZIP code overlaps. The Postal Service may accept other city names in an address, too.
ZIP codes near 51040
| ZIP | City | Distance |
|---|---|---|
51010 | Castana, IA | 8.1 mi |
51523 | Blencoe, IA | 8.1 mi |
51063 | Whiting, IA | 9.3 mi |
68020 | Decatur, NE | 10.9 mi |
51558 | Moorhead, IA | 12.6 mi |
51545 | Little Sioux, IA | 12.8 mi |
51051 | Rodney, IA | 13.1 mi |
51572 | Soldier, IA | 13.8 mi |
68039 | Macy, NE | 15.0 mi |
51026 | Hornick, IA | 15.4 mi |
Find every ZIP code within 10 miles of 51040 →
Questions about this ZIP code
Where is ZIP code 51040?
51040 is in Onawa, Iowa, in Monona County. Its published point location is 42.0325, -96.0687.
What county is 51040 in?
51040 lies in Monona County.
What area code is 51040?
Onawa uses area code 712, from NANPA's telephone records.
What time zone is 51040 in?
51040 uses America/Chicago.
How many people live in 51040?
About 3,500 people live in ZIP code 51040, in 1,555 households, at 27.0 people per square mile. These are American Community Survey 5-year estimates for the ZIP Code Tabulation Area, not a headcount.
What is the median household income in 51040?
$71,179 a year, against $75,059 across Iowa.
What ZIP codes are near 51040?
The closest are 51010 (8.1 mi), 51523 (8.1 mi), 51063 (9.3 mi), 68020 (10.9 mi) and 51558 (12.6 mi).
Is 51040 a PO Box ZIP code?
51040 is a standard ZIP code. A normal ZIP code with street delivery.
Download or cite
Cite this page
zipcodes.pro. “51040 ZIP Code — Onawa, Iowa (Monona County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/51040
Machine-readable version of these facts:
curl https://zipcodes.pro/zip/51040.jsonUnderlying data is public domain or openly licensed — sources, vintages and licences.