21791 ZIP Code, Union Bridge, MD
21791 is a ZIP code in Union Bridge, Maryland — mostly in Frederick County (61% of its land), with smaller parts in Carroll County. It covers 46 square miles of land. The closest ZIP codes are 21762, 21776 and 21757. 5,340 people live here in 1,968 households. With about 116 people per square mile it is lightly settled, and most homes are owner-occupied (82%). Median household income is $93,015, below the Maryland median of $103,678.
Quick facts
- Mailing city: Union Bridge, MD
- County: Frederick County
- Land area: 46 sq mi
- Population: 5,340
- Median household income: $93,015
- Carrier routes: 4 (1,829 homes)
Key figures
| Measure | Value |
|---|---|
| Residents | 5,340 |
| Households | 1,968 |
| Median household income | $93,015 |
| Income per person | $41,286 |
| Median age | 37.7 |
| Homeowners | 81.7% |
| Median home value | $379,800 |
| Median rent | $1,457 |
| Bachelor's degree or higher | 26.7% |
| Average commute (minutes) | 37.3 |
| Households with kids under 18 | 34.5% |
| Moved in the past year | 5.7% |
| Below the poverty line | 5.1% |
| Broadband internet | 85.9% |
| Speak a non-English language at home | 1.9% |
Household income
| % of households | Value |
|---|---|
| <$10K | 1.4% |
| $10–15K | 1.5% |
| $15–25K | 4.5% |
| $25–35K | 4.3% |
| $35–50K | 5.7% |
| $50–75K | 18.6% |
| $75–100K | 19.1% |
| $100–150K | 21.0% |
| $150–200K | 14.7% |
| $200K+ | 9.2% |
Age
| % of all residents | Value |
|---|---|
| <10 | 9.7% |
| 10–19 | 16.4% |
| 20–24 | 6.6% |
| 25–34 | 14.0% |
| 35–44 | 13.2% |
| 45–54 | 7.5% |
| 55–64 | 13.3% |
| 65–74 | 9.5% |
| 75+ | 9.8% |
Tenure
| % of housing units | Value |
|---|---|
| Owned, with mortgage | 61.8% |
| Owned outright | 17.5% |
| Rented | 16.5% |
| Vacant | 4.2% |
Type of building
| % of housing units | Value |
|---|---|
| Detached house | 92.3% |
| Townhome | 1.8% |
| 2–4 units | 3.8% |
| 5–19 units | 1.7% |
| 20+ units | 0.0% |
| Mobile / other | 0.4% |
Businesses in 21791
98 business establishments with 868 employees (ZIP Codes Business Patterns 2023).
- Construction: 33
- Other Services (except Public Administration): 20
- Retail Trade: 7
- Transportation and Warehousing: 6
- Manufacturing: 5
- Administrative and Support and Waste Management and Remediation Services: 5
- Health Care and Social Assistance: 5
- Professional, Scientific, and Technical Services: 4
EDDM carrier routes
21791 has 4 USPS carrier routes with 1,829 residential and 29 business mailboxes. Open the EDDM route map.
Carrier routes in 21791
21791 has 4 USPS carrier routes (4 rural (R)) with 1,829 residential and 29 business mailboxes. Routes range from 415 homes (R004) to 534 homes (R003); the median route has 440 homes. The Census counted 1,968 households in 21791 (2020–2024 average); USPS counts current mailboxes, including new and vacant homes.
| Homes per route | Routes |
|---|---|
| 1–249 | 0 |
| 250–499 | 3 |
| 500–749 | 1 |
| 750–999 | 0 |
| 1,000–1,499 | 0 |
| 1,500+ | 0 |
Best routes in 21791 for…
Most businesses
For B2B offers: office supplies, cleaning, IT, catering and commercial services.
- Route R003 — USPS business mailboxes 12, 534 homes
- Route R004 — USPS business mailboxes 7, 415 homes
- Route R001 — USPS business mailboxes 6, 462 homes
- Route R002 — USPS business mailboxes 4, 418 homes
Select these 4 routes on the route map
Every carrier route in 21791
| Route | Type | Homes | Businesses | Est. median income | Est. owners | Est. families with kids | Est. moved in past year |
|---|---|---|---|---|---|---|---|
| R001 | Rural | 462 | 6 | $108,050 | — | — | — |
| R002 | Rural | 418 | 4 | $108,050 | — | — | — |
| R003 | Rural | 534 | 12 | $68,963 | — | — | — |
| R004 | Rural | 415 | 7 | $68,963 | — | — | — |
Income, owners, families and movers are estimates for each route (how we estimate them); mailbox counts are current USPS figures. Open 21791 on the EDDM route map.
How route demographics are estimated
Mailbox counts come from USPS; demographics are estimates
The number of homes and businesses on each carrier route is the current USPS EDDM count. The Census Bureau does not publish figures for carrier routes, so income, homeownership, ages, families, movers and housing age on a route are EDDM2GO estimates built from Census block groups (neighborhood areas of roughly 600 to 3,000 people).
How a route gets its figures: the block-group length-share method
We trace each route's streets every 25 meters and record which block group each stretch falls in. The route's homes are spread along its streets in proportion to length, so a route with 60% of its street length in one block group is assumed to have 60% of its homes there. Each block group then contributes its Census counts in proportion to the share of its housing units that sit on the route (capped at the whole block group). Medians are recalculated from the combined income, home-value and age brackets, the way the Census Bureau computes them, not averaged.
Margins of error
Census survey figures carry a margin of error at 90% confidence; we carry it through the calculation and show it as ±. Our margins treat the route-to-block-group split as exact, so the real uncertainty is larger. Routes with fewer than 100 estimated households, large margins, or streets we could not place are flagged.
Different years
USPS mailbox counts are current. Census figures are 5-year averages for 2020–2024, so a new subdivision may have more homes on the route today than the Census counted. Use the route figures to compare routes with each other, not as an exact head count.
Why some routes show identical figures
Two routes that run through the same block group get the same percentages and medians, because the Census publishes one set of figures for the whole block group. Their mailbox counts still differ, and those are exact.
Route and mailbox counts: USPS EDDM route data. Route demographics: EDDM2GO estimates from U.S. Census Bureau American Community Survey 5-year block-group data (2020–2024) and 2024 cartographic block-group boundaries. This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.
Nearby ZIP codes
- 21762 — Libertytown CDP, MD (4.8 mi)
- 21776 — New Windsor town, MD (4.8 mi)
- 21757 (5.6 mi)
- 21798 — Woodsboro town, MD (5.7 mi)
- 21793 — Walkersville town, MD (8.8 mi)
- 21778 (9.4 mi)
- 21774 — Linganore CDP, MD (9.6 mi)
- 21771 — Green Valley CDP, MD (9.7 mi)
Areas that include 21791
- Libertytown, MD ZIP codes — 3 ZIP codes
- Union Bridge, MD ZIP codes — 1 ZIP code
- Carroll County ZIP codes — 14 ZIP codes
- Frederick County ZIP codes — 33 ZIP codes
- Maryland ZIP code data
Where it ranks
Mail every home in 21791
Route counts on this page price as Full Service 6.5 × 9 postcards: we print, bundle by carrier route and hand the mailing to USPS. Prefer to take it to the Post Office yourself? Print only costs less and you pay postage at drop-off.
EDDM guides
ZIP code statistics describe the Census ZIP Code Tabulation Area (ZCTA) 21791, which approximates the USPS ZIP code area. Census figures: American Community Survey 5-year estimates, 2020–2024.
Frequently asked questions
- What city is 21791 in?
- 21791 is a Union Bridge, MD mailing address. By land area, 2% lies inside Union Bridge and 2% lies inside Libertytown; the rest is outside any Census-defined city or community.
- What county is 21791 in?
- 21791 is mostly in Frederick County (61% of its land), with smaller parts in Carroll County.
- What is the population of 21791?
- About 5,340 people (±843), according to the Census Bureau's American Community Survey 5-year estimates for 2020–2024. The 2020 Census counted 5,292.
- What is the median household income in 21791?
- $93,015 (±$9,656), compared with $103,678 for Maryland as a whole. Half the households in the ZIP code earn more and half earn less.
- How many carrier routes and mailboxes are in 21791?
- 4 USPS carrier routes with 1,829 residential and 29 business mailboxes (1,858 in all), from the route data stored by EDDM2GO. An EDDM mailing can target any combination of these routes.
- What ZIP codes are near 21791?
- The closest, measured center to center: 21762 (4.8 mi, Libertytown), 21776 (4.8 mi, New Windsor), 21757 (5.6 mi), 21798 (5.7 mi, Woodsboro), 21793 (8.8 mi, Walkersville) and 21778 (9.4 mi).
This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.