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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/21639

21639

ZIP 21639 is Greensboro, Maryland, in Caroline County; area codes 667 and 410; Eastern time.

Type
Standard
Time zone
America/New_York
County
Caroline
Metro area
none
Population
4,682
Coordinates
38.9587, -75.7825
☼ Live from 21639 — Greensboro, MD

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Local time: —

Where 21639 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.

★ Weird and wonderful facts about 21639
  • 🔢 Type 21639 into a pocket calculator and turn it upside down: GEgIZ — not quite a word, sorry.
  • ➕ As a number, 21,639 = 3 × 7213. Its digits add up to 21, a total 2,594 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 101010010000111
  • 🏠 Its numerical neighbours: 21638 (Grasonville, MD, 23 mi away) and 21640 (Henderson, MD, 8 mi away).
  • 🔄 Backwards, 21639 becomes 93612 — and that is a real ZIP code: Clovis, CA, 2,377 miles away.
  • 👥 44 other ZIP codes are made of exactly the same digits (12936, 13692, 16239, 16329, 16923, 16932, …). The farthest-flung twin is 96321 in FPO AA, a military post office, 7,193 miles away.
  • 🧭 Farther south than 51% of all ZIP codes, and farther east than 85%.
  • 🎯1,215 miles east of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 21639 and you would come out at 38.96°S, 104.22°E — 814 miles from Perth, Australia, the nearest big city to that spot.
  • ☀Longest day of the year: 14h 54m of daylight. Shortest: 9h 26m.
  • 📏 At 33.1 square miles of land, 21639 is bigger than 48% of ZIP codes — room for about 25 Central Parks.
🌙 The sky over 21639 today
  • Working out the sun…
🌋 Shake report
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Source: USGS.

People and housing

Population4,682This ZIP4,682
Households1,743This ZIP1,743
Housing units1,916This ZIP1,916
Median age37.7This ZIP37.7Maryland39.4US 38.9
Median household income$62,772This ZIP$62,772Maryland$103,678US $80,734
Median home value$269,400This ZIP$269,400Maryland$419,900US $332,700
Median gross rent$1,107This ZIP$1,107Maryland$1,705US $1,413
Bachelor's degree or higher13.5%This ZIP13.5%
Mean commute38.8 minThis ZIP38.8 min
Population density141.5 / sq miThis ZIP141.5 / sq mi

Business and tax activity

Business establishments73This ZIP73
Employees403This ZIP403
Annual payroll$17,262,000This ZIP$17,262,000
Tax returns filed2,260This ZIP2,260
Total adjusted gross income$134,096,000This ZIP$134,096,000

Land area

Land area33.09 sq miThis ZIP33.09 sq mi
Water area0.32 sq miThis ZIP0.32 sq mi

Other place names in 21639

Census places whose land this ZIP code overlaps. The Postal Service may accept other city names in an address, too.

ZIP codes near 21639

ZIPCityDistance
21636 Goldsboro, MD 4.0 mi
21660 Ridgely, MD 5.7 mi
21629 Denton, MD 7.3 mi
21640 Henderson, MD 7.8 mi
21641 Hillsboro, MD 9.0 mi
19952 Harrington, DE 9.6 mi
19943 Felton, DE 9.9 mi
19964 Marydel, DE 10.0 mi
21657 Queen Anne, MD 10.8 mi
21644 Ingleside, MD 12.0 mi

Find every ZIP code within 10 miles of 21639 →

Questions about this ZIP code

Where is ZIP code 21639?

21639 is in Greensboro, Maryland, in Caroline County. Its published point location is 38.9587, -75.7825.

What county is 21639 in?

21639 lies in Caroline County.

What area code is 21639?

Greensboro uses area codes 667 and 410, from NANPA's telephone records.

What time zone is 21639 in?

21639 uses America/New_York.

How many people live in 21639?

About 4,682 people live in ZIP code 21639, in 1,743 households, at 141.5 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 21639?

$62,772 a year, against $103,678 across Maryland.

What ZIP codes are near 21639?

The closest are 21636 (4 mi), 21660 (5.7 mi), 21629 (7.3 mi), 21640 (7.8 mi) and 21641 (9 mi).

Is 21639 a PO Box ZIP code?

21639 is a standard ZIP code. A normal ZIP code with street delivery.

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Cite this page

zipcodes.pro. “21639 ZIP Code — Greensboro, Maryland (Caroline County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/21639

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