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zipcodes.pro — ZIP/21791

21791

ZIP 21791 is Union Bridge, Maryland, mostly in Frederick County; area codes 443, 410 and 667; Eastern time.

Type
Standard
Time zone
America/New_York
County
Frederick +1 more
Population
5,340
Coordinates
39.5331, -77.1886
☼ Live from 21791 — Union Bridge, MD

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Local time: —

Where 21791 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 21791
  • 🔢 Type 21791 into a pocket calculator and turn it upside down: IGLIZ — not quite a word, sorry.
  • ➕ As a number, 21,791 = 7 × 11 × 283. Its digits add up to 20, a total 2,586 other ZIP codes share.
  • 💾In binary, the way a computer stores it: 101010100011111
  • 🏠 Its numerical neighbours: 21790 (Tuscarora, MD, 25 mi away) and 21792 (Unionville, MD, 4 mi away).
  • 🔄 Backwards, 21791 becomes 19712 — and that is a real ZIP code: Newark, DE, 85 miles away.
  • 👥 30 other ZIP codes are made of exactly the same digits (11729, 11792, 11972, 12197, 12719, 12791, …). The farthest-flung twin is 97112 in Cloverdale, OR, 2,381 miles away.
  • 🧭 Farther north than 52% of all ZIP codes, and farther east than 81%.
  • 🎯1,135 miles east of the geographic center of the Lower 48, near Lebanon, Kansas.
  • 🌏 Dig straight through the Earth from 21791 and you would come out at 39.53°S, 102.81°E — 898 miles from Perth, Australia, the nearest big city to that spot.
  • ☀Longest day of the year: 14h 58m of daylight. Shortest: 9h 22m.
  • 📏 At 46.0 square miles of land, 21791 is bigger than 57% of ZIP codes — room for about 35 Central Parks.
🌙 The sky over 21791 today
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🌋 Shake report
  • Checking the USGS…

Source: USGS.

People and housing

Population5,340This ZIP5,340
Households1,968This ZIP1,968
Housing units2,059This ZIP2,059
Median age37.7This ZIP37.7Maryland39.4US 38.9
Median household income$93,015This ZIP$93,015Maryland$103,678US $80,734
Median home value$379,800This ZIP$379,800Maryland$419,900US $332,700
Median gross rent$1,457This ZIP$1,457Maryland$1,705US $1,413
Bachelor's degree or higher26.7%This ZIP26.7%
Mean commute37.3 minThis ZIP37.3 min
Population density116.0 / sq miThis ZIP116.0 / sq mi

Business and tax activity

Business establishments98This ZIP98
Employees868This ZIP868
Annual payroll$40,869,000This ZIP$40,869,000
Tax returns filed2,560This ZIP2,560
Total adjusted gross income$218,414,000This ZIP$218,414,000

Land area

Land area46.04 sq miThis ZIP46.04 sq mi
Water area0.08 sq miThis ZIP0.08 sq mi

Counties 21791 spans

A ZIP code is a mail route and ignores county lines. Shares are by overlapping land area.

CountyShare of this ZIP
Frederick County 60.7%
Carroll County 39.3%

Other place names in 21791

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

ZIP codes near 21791

ZIPCityDistance
21792 Unionville, MD 4.0 mi
21762 Libertytown, MD 4.8 mi
21776 New Windsor, MD 4.8 mi
21757 Keymar, MD 5.6 mi
21798 Woodsboro, MD 5.7 mi
21759 Ladiesburg, MD 6.0 mi
21775 New Midway, MD 6.1 mi
21793 Walkersville, MD 8.8 mi
21778 Rocky Ridge, MD 9.4 mi
21774 New Market, MD 9.6 mi

Find every ZIP code within 10 miles of 21791 →

Questions about this ZIP code

Where is ZIP code 21791?

21791 is in Union Bridge, Maryland, in Frederick County, part of the Washington-Arlington-Alexandria, DC-VA-MD-WV metropolitan area. Its published point location is 39.5331, -77.1886.

What county is 21791 in?

21791 spans 2 counties: Frederick County and Carroll County. Most of it falls in Frederick County, measured by overlapping land area — the county holding the most land in a ZIP code is not always the one holding the most residents.

What area code is 21791?

Union Bridge uses area codes 443, 410 and 667, from NANPA's telephone records.

What time zone is 21791 in?

21791 uses America/New_York.

How many people live in 21791?

About 5,340 people live in ZIP code 21791, in 1,968 households, at 116.0 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 21791?

$93,015 a year, against $103,678 across Maryland.

What ZIP codes are near 21791?

The closest are 21792 (4 mi), 21762 (4.8 mi), 21776 (4.8 mi), 21757 (5.6 mi) and 21798 (5.7 mi).

Is 21791 a PO Box ZIP code?

21791 is a standard ZIP code. A normal ZIP code with street delivery.

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Cite this page

zipcodes.pro. “21791 ZIP Code — Union Bridge, Maryland (Frederick County).” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/zip/21791

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