21104 ZIP Code, Marriottsville, MD
21104 is a ZIP code in Marriottsville, Maryland — mostly in Howard County (53% of its land), with smaller parts in Carroll and Baltimore counties. It covers 17 square miles of land. The closest ZIP codes are 21163, 21794 and 21042. 6,052 people live here in 2,097 households. With about 355 people per square mile it is lightly settled, and most homes are owner-occupied (97%). Median household income is $191,804, well above the Maryland median of $103,678.
Quick facts
- Mailing city: Marriottsville, MD
- County: Howard County
- Land area: 17 sq mi
- Population: 6,052
- Median household income: $191,804
- Carrier routes: 6 (2,277 homes)
Key figures
| Measure | Value |
|---|---|
| Residents | 6,052 |
| Households | 2,097 |
| Median household income | $191,804 |
| Income per person | $74,405 |
| Median age | 43.1 |
| Homeowners | 97.0% |
| Median home value | $680,200 |
| Median rent | $1,384 |
| Bachelor's degree or higher | 64.4% |
| Average commute (minutes) | 31.9 |
| Households with kids under 18 | 34.6% |
| Moved in the past year | 8.3% |
| Below the poverty line | 2.7% |
| Broadband internet | 98.9% |
| Speak a non-English language at home | 17.4% |
Household income
| % of households | Value |
|---|---|
| <$10K | 0.2% |
| $10–15K | 0.0% |
| $15–25K | 1.3% |
| $25–35K | 2.8% |
| $35–50K | 5.4% |
| $50–75K | 6.1% |
| $75–100K | 7.9% |
| $100–150K | 14.0% |
| $150–200K | 15.4% |
| $200K+ | 46.9% |
Age
| % of all residents | Value |
|---|---|
| <10 | 10.4% |
| 10–19 | 11.9% |
| 20–24 | 6.7% |
| 25–34 | 8.4% |
| 35–44 | 15.2% |
| 45–54 | 11.8% |
| 55–64 | 17.6% |
| 65–74 | 12.1% |
| 75+ | 5.9% |
Tenure
| % of housing units | Value |
|---|---|
| Owned, with mortgage | 69.3% |
| Owned outright | 23.1% |
| Rented | 2.8% |
| Vacant | 4.8% |
Type of building
| % of housing units | Value |
|---|---|
| Detached house | 89.2% |
| Townhome | 7.8% |
| 2–4 units | 0.0% |
| 5–19 units | 2.9% |
| 20+ units | 0.0% |
| Mobile / other | 0.0% |
Businesses in 21104
157 business establishments with 1,322 employees (ZIP Codes Business Patterns 2023).
- Professional, Scientific, and Technical Services: 40
- Construction: 20
- Health Care and Social Assistance: 16
- Finance and Insurance: 11
- Administrative and Support and Waste Management and Remediation Services: 11
- Other Services (except Public Administration): 11
- Real Estate and Rental and Leasing: 10
- Wholesale Trade: 9
EDDM carrier routes
21104 has 6 USPS carrier routes with 2,277 residential and 131 business mailboxes. Open the EDDM route map.
Carrier routes in 21104
21104 has 6 USPS carrier routes (6 rural (R)) with 2,277 residential and 131 business mailboxes. Routes range from 61 homes (R031) to 546 homes (R102); the median route has 426 homes. The Census counted 2,097 households in 21104 (2020–2024 average); USPS counts current mailboxes, including new and vacant homes.
| Homes per route | Routes |
|---|---|
| 1–249 | 1 |
| 250–499 | 4 |
| 500–749 | 1 |
| 750–999 | 0 |
| 1,000–1,499 | 0 |
| 1,500+ | 0 |
Best routes in 21104 for…
Most businesses
For B2B offers: office supplies, cleaning, IT, catering and commercial services.
- Route R108 — USPS business mailboxes 108, 356 homes
- Route R107 — USPS business mailboxes 12, 432 homes
- Route R109 — USPS business mailboxes 7, 420 homes
- Route R104 — USPS business mailboxes 4, 462 homes
Select these 4 routes on the route map
Every carrier route in 21104
| Route | Type | Homes | Businesses | Est. median income | Est. owners | Est. families with kids | Est. moved in past year |
|---|---|---|---|---|---|---|---|
| R031 | Rural | 61 | 0 | $95,635 | — | — | — |
| R102 | Rural | 546 | 0 | $200,000+ | — | — | — |
| R104 | Rural | 462 | 4 | $180,140 | — | — | — |
| R107 | Rural | 432 | 12 | $185,529 | — | — | — |
| R108 | Rural | 356 | 108 | $180,140 | — | — | — |
| R109 | Rural | 420 | 7 | $185,529 | — | — | — |
Income, owners, families and movers are estimates for each route (how we estimate them); mailbox counts are current USPS figures. Open 21104 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
- 21163 — Randallstown CDP, MD (3.5 mi)
- 21794 (4.4 mi)
- 21042 — Ellicott City CDP, MD (4.9 mi)
- 21723 (5 mi)
- 21784 — Eldersburg CDP, MD (5 mi)
- 21133 — Randallstown CDP, MD (5.8 mi)
- 21136 — Reisterstown CDP, MD (7.3 mi)
- 21244 — Milford Mill CDP, MD (7.3 mi)
Areas that include 21104
- Eldersburg, MD ZIP codes — 2 ZIP codes
- Marriottsville, MD ZIP codes — 1 ZIP code
- Baltimore County ZIP codes — 54 ZIP codes
- Carroll County ZIP codes — 14 ZIP codes
- Howard County ZIP codes — 24 ZIP codes
- Maryland ZIP code data
Where it ranks
Mail every home in 21104
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) 21104, which approximates the USPS ZIP code area. Census figures: American Community Survey 5-year estimates, 2020–2024.
Frequently asked questions
- What city is 21104 in?
- 21104 is a Marriottsville, MD mailing address. By land area, 32% lies inside Eldersburg and 3% lies inside Ellicott City; the rest is outside any Census-defined city or community.
- What county is 21104 in?
- 21104 is mostly in Howard County (53% of its land), with smaller parts in Carroll and Baltimore counties.
- What is the population of 21104?
- About 6,052 people (±883), according to the Census Bureau's American Community Survey 5-year estimates for 2020–2024. The 2020 Census counted 5,686.
- What is the median household income in 21104?
- $191,804 (±$9,742), 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 21104?
- 6 USPS carrier routes with 2,277 residential and 131 business mailboxes (2,408 in all), from the route data stored by EDDM2GO. An EDDM mailing can target any combination of these routes.
- What ZIP codes are near 21104?
- The closest, measured center to center: 21163 (3.5 mi, Randallstown), 21794 (4.4 mi), 21042 (4.9 mi, Ellicott City), 21723 (5 mi), 21784 (5 mi, Eldersburg) and 21133 (5.8 mi, Randallstown).
This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.