21639 ZIP Code, Greensboro, MD
21639 is a ZIP code in Greensboro, Maryland in Caroline County. It covers 33 square miles of land. The closest ZIP codes are 21636, 21660 and 21629. 4,682 people live here in 1,743 households. With about 142 people per square mile it is lightly settled, and most homes are owner-occupied (72%). Median household income is $62,772, well below the Maryland median of $103,678.
Quick facts
- Mailing city: Greensboro, MD
- County: Caroline County
- Land area: 33 sq mi
- Population: 4,682
- Median household income: $62,772
- Carrier routes: 3 (1,797 homes)
Key figures
| Measure | Value |
|---|---|
| Residents | 4,682 |
| Households | 1,743 |
| Median household income | $62,772 |
| Income per person | $33,990 |
| Median age | 37.7 |
| Homeowners | 72.2% |
| Median home value | $269,400 |
| Median rent | $1,107 |
| Bachelor's degree or higher | 13.5% |
| Average commute (minutes) | 38.8 |
| Households with kids under 18 | 36.5% |
| Moved in the past year | 8.2% |
| Below the poverty line | 10.3% |
| Broadband internet | 87.0% |
| Speak a non-English language at home | 17.8% |
Household income
| % of households | Value |
|---|---|
| <$10K | 2.7% |
| $10–15K | 1.0% |
| $15–25K | 7.9% |
| $25–35K | 18.6% |
| $35–50K | 8.6% |
| $50–75K | 18.2% |
| $75–100K | 10.1% |
| $100–150K | 19.3% |
| $150–200K | 9.1% |
| $200K+ | 4.5% |
Age
| % of all residents | Value |
|---|---|
| <10 | 14.8% |
| 10–19 | 12.7% |
| 20–24 | 7.4% |
| 25–34 | 11.7% |
| 35–44 | 12.9% |
| 45–54 | 12.0% |
| 55–64 | 12.7% |
| 65–74 | 8.9% |
| 75+ | 6.9% |
Tenure
| % of housing units | Value |
|---|---|
| Owned, with mortgage | 44.9% |
| Owned outright | 22.2% |
| Rented | 24.3% |
| Vacant | 8.7% |
Type of building
| % of housing units | Value |
|---|---|
| Detached house | 78.0% |
| Townhome | 5.1% |
| 2–4 units | 6.4% |
| 5–19 units | 2.4% |
| 20+ units | 2.9% |
| Mobile / other | 5.2% |
Businesses in 21639
73 business establishments with 403 employees (ZIP Codes Business Patterns 2023).
- Construction: 21
- Retail Trade: 12
- Other Services (except Public Administration): 7
- Accommodation and Food Services: 6
- Health Care and Social Assistance: 5
- Wholesale Trade: 4
- Administrative and Support and Waste Management and Remediation Services: 4
- Manufacturing: 3
EDDM carrier routes
21639 has 3 USPS carrier routes with 1,797 residential and 36 business mailboxes. Open the EDDM route map.
Carrier routes in 21639
21639 has 3 USPS carrier routes (3 rural (R)) with 1,797 residential and 36 business mailboxes. Routes range from 514 homes (R393) to 708 homes (R392); the median route has 575 homes. The Census counted 1,743 households in 21639 (2020–2024 average); USPS counts current mailboxes, including new and vacant homes.
| Homes per route | Routes |
|---|---|
| 1–249 | 0 |
| 250–499 | 0 |
| 500–749 | 3 |
| 750–999 | 0 |
| 1,000–1,499 | 0 |
| 1,500+ | 0 |
Best routes in 21639 for…
Most businesses
For B2B offers: office supplies, cleaning, IT, catering and commercial services.
- Route R393 — USPS business mailboxes 19, 514 homes
- Route R391 — USPS business mailboxes 10, 575 homes
- Route R392 — USPS business mailboxes 7, 708 homes
Select these 3 routes on the route map
Every carrier route in 21639
| Route | Type | Homes | Businesses | Est. median income | Est. owners | Est. families with kids | Est. moved in past year |
|---|---|---|---|---|---|---|---|
| R391 | Rural | 575 | 10 | $83,076 | — | — | — |
| R392 | Rural | 708 | 7 | $71,721 | — | — | — |
| R393 | Rural | 514 | 19 | $71,721 | — | — | — |
Income, owners, families and movers are estimates for each route (how we estimate them); mailbox counts are current USPS figures. Open 21639 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
- 21636 — Goldsboro town, MD (4 mi)
- 21660 — Ridgely town, MD (5.7 mi)
- 21629 — Denton town, MD (7.3 mi)
- 21640 — Henderson town, MD (7.8 mi)
- 21641 — Hillsboro town, MD (9 mi)
- 19952 — Harrington city, DE (9.6 mi)
- 19943 — Riverview CDP, DE (9.9 mi)
- 19964 (10 mi)
Areas that include 21639
- Greensboro, MD ZIP codes — 1 ZIP code
- Caroline County ZIP codes — 9 ZIP codes
- Maryland ZIP code data
Where it ranks
- No. 5 of 8: highest median home value in Caroline County
- No. 2 of 8: highest share of households with children in Caroline County
- No. 5 of 8: highest share of residents who moved in during the past year in Caroline County
- No. 3 of 8: lowest median age in Caroline County
Mail every home in 21639
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) 21639, which approximates the USPS ZIP code area. Census figures: American Community Survey 5-year estimates, 2020–2024.
Frequently asked questions
- What city is 21639 in?
- 21639 is a Greensboro, MD mailing address. By land area, 3% lies inside Greensboro; the rest is outside any Census-defined city or community.
- What county is 21639 in?
- 21639 is in Caroline County.
- What is the population of 21639?
- About 4,682 people (±528), according to the Census Bureau's American Community Survey 5-year estimates for 2020–2024. The 2020 Census counted 4,354.
- What is the median household income in 21639?
- $62,772 (±$19,053), 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 21639?
- 3 USPS carrier routes with 1,797 residential and 36 business mailboxes (1,833 in all), from the route data stored by EDDM2GO. An EDDM mailing can target any combination of these routes.
- What ZIP codes are near 21639?
- The closest, measured center to center: 21636 (4 mi, Goldsboro), 21660 (5.7 mi, Ridgely), 21629 (7.3 mi, Denton), 21640 (7.8 mi, Henderson), 21641 (9 mi, Hillsboro) and 19952 (9.6 mi, Harrington).
This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.