Every ZIP code in the United States, with weather, radar, trivia and the numbers behind it. Five digits since 1963!

ZIP stands for Zone Improvement Plan. The codes went live on July 1, 1963.The lowest ZIP code is 00501 — the IRS in Holtsville, New York.The highest ZIP code is 99950, in Ketchikan, Alaska.Type 07734 into a calculator and turn it upside down: hELLO. It is Keansburg, New Jersey.12345 belongs to one company: General Electric in Schenectady, New York.The first digit is a region: 0 is New England and New Jersey, 9 is the West Coast, Alaska and Hawaii.Mr. ZIP, the cartoon mailman, was the mascot that sold the idea to America.ZIP+4 arrived in 1983 and can narrow a ZIP down to one side of one block.A ZIP code is a mail route, not a place: plenty of them cross county and even state lines.Play ZIP Hunt: guess the secret ZIP code of the day in six tries.
zipcodes.pro — ZIP/51591

51591

ZIP 51591 is in Red Oak, Iowa, in Montgomery County; area code 712; Central time. Red Oak has 2 ZIP codes; the other is 51566.

Type
No street area
Time zone
America/Chicago
County
Montgomery
Metro area
none
Coordinates
41.0303, -95.1562

The Census map gives this ZIP code no delivery area of its own, which usually means it serves post office boxes, a single organization or a post office rather than streets of homes.

This ZIP code has no Census tabulation area of its own. Its point falls inside ZCTA 51566, whose figures describe that area — not this ZIP code.

☼ Live from 51591 — Red Oak, IA

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Where 51591 is

This ZIP code has no Census tabulation area, so there is no boundary to draw — the marker is its published point location.

★ Weird and wonderful facts about 51591
  • 🔢 Type 51591 into a pocket calculator and turn it upside down: IGSIS — not quite a word, sorry.
  • ➕ As a number, 51,591 = 3 × 29 × 593. Its digits add up to 21, a total 2,594 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 1100100110000111
  • 🏠 Its numerical neighbours: 51579 (Woodbine, IA, 58 mi away) and 51593 (Harlan, IA, 34 mi away).
  • 🔄 Backwards, 51591 becomes 19515, which is not a ZIP code at all.
  • 👥 11 other ZIP codes are made of exactly the same digits (11559, 11955, 15915, 15951, 19155, 19551, …). The farthest-flung twin is 95511 in Alderpoint, CA, 1,486 miles away.
  • 🧭 Farther north than 67% of all ZIP codes, and farther west than 69%.
  • 🎯198 miles northeast of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 51591 and you would come out at 41.03°S, 84.84°E — 912 miles from Port-aux-Français, French Southern Territories, the nearest big city to that spot.
  • ☀Longest day of the year: 15h 08m of daylight. Shortest: 9h 13m.
🌙 The sky over 51591 today
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Source: USGS.

Land area

ZIP codes near 51591

ZIPCityDistance
51566 Red Oak, IA 4.0 mi
51573 Stanton, IA 4.8 mi
51532 Elliott, IA 7.8 mi
50864 Villisca, IA 10.2 mi
51533 Emerson, IA 11.6 mi
50847 Grant, IA 11.8 mi
51535 Griswold, IA 13.6 mi
51638 Essex, IA 14.5 mi
51541 Henderson, IA 15.5 mi
50857 Nodaway, IA 15.9 mi

Find every ZIP code within 10 miles of 51591 →

Questions about this ZIP code

Where is ZIP code 51591?

51591 is in Red Oak, Iowa, in Montgomery County. Its published point location is 41.0303, -95.1562.

What county is 51591 in?

51591 lies in Montgomery County.

What area code is 51591?

Red Oak uses area code 712, from NANPA's telephone records.

What time zone is 51591 in?

51591 uses America/Chicago.

What ZIP codes are near 51591?

The closest are 51566 (4 mi), 51573 (4.8 mi), 51532 (7.8 mi), 50864 (10.2 mi) and 51533 (11.6 mi).

Is 51591 a PO Box ZIP code?

Possibly. The Census map gives this ZIP code no delivery area of its own, which usually means it serves post office boxes, a single organization or a post office rather than streets of homes.

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Cite this page

zipcodes.pro. “51591 ZIP Code — Red Oak, Iowa (Montgomery County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/51591

Machine-readable version of these facts:

curl https://zipcodes.pro/zip/51591.json

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