Residential delivery area · Maryland
ZIP Code 21770: Green Valley (Monrovia), MD
ZIP code 21770 is in Green Valley (postal name Monrovia), Maryland, entirely in Frederick County (Census 2020 ZIP-county file). About 8,800 people live there (Census Bureau, ACS 2020-2024). Median household income is $183,571 (Census Bureau, ACS 2020-2024). By Census place, its land lies in Green Valley (60%) and Monrovia (20%), and 2% in smaller places; 18% is outside any Census place.
- ACS2020-24
- Census2020
- FHFA2025
- ZBP2023
- IRS2022
- Town
- Monrovia · its only residential ZIP
- County
- Frederick County
- Census places
- Green Valley (60%) census-designated place; Monrovia (20%) census-designated place
- Metro area
- Washington-Arlington-Alexandria, DC-VA-MD-WV
- House district
- MD-6 119th Congress
- State
- Maryland
- Time zone
- Eastern
- Land area
- 11.5 sq mi · 764 people per sq mi
Where is ZIP code 21770?
21770 centers on 39.350°, -77.256° and covers 11.5 square miles of land plus 0.0 of water. It borders 4 ZIP codes: 21754, 21774, 20872, 21771.
The map draws ZIP code areas only. For the streets inside 21770, open its center on OpenStreetMap.
Source: U.S. Census Bureau, 2020 ZCTA cartographic boundaries and the 2023 Gazetteer (2020 ZCTAs); ZIP-to-county shares, Census places and House districts (119th Congress) from the Census 2020 relationship files (shares of land); metro area from the OMB delineation (July 2023); town name and time zone from simplemaps US ZIP Codes (CC BY 4.0).
How does 21770 compare with the rest of Frederick County?
| Measure | 21770 | In Frederick County | In MD |
|---|---|---|---|
| People (ACS 2020-2024) | 8,751 | 13th of 35 | 193rd of 477 |
| Median household income | $184k | 2nd of 26 | 22nd of 293 |
| Median home value | $633k | 4th of 28 | 40th of 320 |
Its median household income is higher than in 99% of U.S. residential ZIP codes, and it is denser than 76% of all U.S. residential ZIP codes. ZIP codes at the ACS caps ($250,000 or more for household income, $2,000,000 or more for home value) share the top rank.
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B01003, B19013, B25077); ranks by PlainZIP over residential ZIP codes (ZCTAs).
How many people live in 21770?
The 2020 Census counted 7,575 people in 21770; the ACS, which samples households over 2020-2024, estimates 8,751. Between the 2010 and 2020 censuses its population grew 46.7% (its boundary stayed at least 90% the same).
- People, ACS 2020-2024
- 8,751±1,309 (90% margin)
- 2020 Census count
- 7,575+46.7% since 2010 (5,164)
- Households
- 2,622
- Median age
- 39.8
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B01003, B01002, B11001); 2020 Census (DHC P1); 2010 Census (SF1 P1).
Who lives in 21770?
Of the 8,751 people the ACS estimates in 21770, 22.5% are under 18 and 17.7% are 65 or older. The largest group by race and Hispanic origin is White (not Hispanic) (72.3%), then Asian (not Hispanic) (12.3%).
- Under 1822.5%
- 18 to 6459.8%
- 65 and older17.7%
- White, not Hispanic72.3%
- Asian, not Hispanic12.3%
- Black, not Hispanic7.9%
- Other or two or more4.5%
- Hispanic or Latino3.1%
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B01001 age by sex, B03002 Hispanic or Latino origin by race); shares of the estimated population, small ZIP codes carry wide margins.
What do households in 21770 earn?
Median household income is $183,571 (ACS 2020-2024), the 2nd highest of the 26 ranked ZIP codes in Frederick County. It is not measurably different from 2015-2019 ($170,245 in 2024 dollars): the change is within the surveys' margins of error.
- Median household income
- $183,571±$20,324
- Income per person
- $58,954
- Below the poverty line
- 1.5%
- Unemployed (of the labor force)
- 2.8%
- Adults 25+ with a bachelor's degree
- 54.8%
- Adjusted gross income per tax return, 2022
- $131,9944,120 returns; wages 79% of AGI (IRS)
Source: U.S. Census Bureau, ACS 2020-2024 and 2015-2019 5-year estimates (B19013, B19301, B17001, B23025, B15003; 2015-2019 dollars converted with the BLS CPI-U, 1.22699); IRS Statistics of Income, ZIP code data, tax year 2022 (adjusted gross income per return, filed under the address on the return).
What are homes worth in 21770?
FHFA's house price index for 21770, built from repeat sales and appraisals of the same homes, rose 69% from 2015 to 2025 and rose 43% from 2020 to 2025, and moved +2.7% in 2025.
- Median home value (owners' estimate)
- $632,500
- Median gross rent
- –
- Homes owned by their occupants
- 98.8%
- Housing units
- 2,632
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B25077, B25064, B25003, B25001); FHFA House Price Index, annual five-digit ZIP, updated 2026-03-31.
What businesses are in 21770?
150 business establishments had a location in this ZIP code in 2023, 36 more than in 2018; the most are in construction (ZIP Code Business Patterns).
- Construction40
- Professional, scientific, and technical services34
- Retail trade10
- Administrative and support and waste management and remediation services10
- Health care and social assistance10
- Other services (except public administration)10
Source: U.S. Census Bureau, ZIP Code Business Patterns 2023 and 2018 (establishments with paid employees, by the business's ZIP code).
Which ZIP codes are next to 21770?
| ZIP | Town | People | Household income | Distance |
|---|---|---|---|---|
| 21754 | Ijamsville | 8,156 | $182k | 3.4 mi |
| 21774 | New Market | 17,134 | $171k | 4.3 mi |
| 20872 | Damascus | 13,983 | $141k | 4.4 mi |
| 21771 | Mount Airy | 33,031 | $157k | 6.1 mi |
| 21704 | Frederick | 20,006 | $161k | 6.4 mi (near) |
| 20871 | Clarksburg | 30,182 | $178k | 6.5 mi (near) |
| 21701 | Frederick | 43,048 | $107k | 7.6 mi (near) |
| 21762 | Libertytown | 139 | – | 9.0 mi (near) |
Source: PlainZIP from the Census 2020 ZCTA boundaries (shared edges) and internal points; figures ACS 2020-2024.