21771 ZIP Code Profile, Map, Data & Demographics

ZIP Code Type: STANDARD
County: Frederick County
Centroid: Latitude 39.388, Longitude -77.148
Time Zone: Eastern Time Zone (UTC -5 hours)
Observes DST: Yes

ZIP Code 21771 has segments in 4 Counties / Independent Cities (Carroll, Frederick, Howard, Montgomery).

Businesses Addresses: 731
PO Box Addresses: 230
Residential Addresses: 11,033

Multi-Family Addresses: 106
Single Family Addresses: 10,927

The ZIP Code maps and database are updated 4 times per year.
Database updated: October 1, 2025, Maps updated: May 1, 2024.

Mount Airy, MD 21771 Data & Demographics (As of July 1, 2025)

POPULATION
Total Population	30,810 (100%)
Population in Households	30,671 (99.5%)
Population in Families	26,942 (87.4%)
Population in Group Quarters¹	139 ( 0.5%)
Population Density	373
Diversity Index²	40


INCOME
Median Household Income	$159,481
Average Household Income	$183,386
% of Income for Mortgage⁴	24%
Per Capita Income	$64,039
Wealth Index⁵	204
Socioeconomic Status Index⁶	Moderate (60.7)

HOUSING
Total HU (Housing Units)	11,026 (100%)
Owner Occupied HU	9,862 (89.4%)
Renter Occupied HU	893 ( 8.1%)
Vacant Housing Units	271 ( 2.5%)
Median Home Value	$598,074
Average Home Value	$618,694
Housing Affordability Index³	100

HOUSEHOLDS
Total Households	10,755
Average Household Size	2.85
Family Households	8,490
Average Family Size	3.00

NOTES

Group Quarters - a place where people live or stay in a group living arrangement. Includes college residents halls, nursing facilities, military barracks, and correctional facilities.
The Diversity Index is a scale of 0 to 100 that represents the likelihood that two persons, chosen at random from the same area, belong to different races or ethnic groups. If an area's entire population belongs to one race AND one ethnic group, then the area has zero diversity. An area's diversity index increases to 100 when the population is evenly divided into two or more race/ethnic groups.
The Housing Affordability Index base is 100 and represents a balance point where a resident with a median household income can normally qualify to purchase a median price home. Values above 100 indicate increased affordability, while values below 100 indicate decreased affordability.
The % of Income for Mortgage quantifies the percentage of median household income dedicated to mortgage payments on a home priced at the median value (assuming a 30-year mortgage and a 20% down payment).
The Wealth Index is based on a number of indicators of affluence including average household income and average net worth, but it also includes the value of material possessions and resources. It represents the wealth of the area relative to the national level. Values above or below 100 represent above-average wealth or below-average wealth compared to the national level.
The Socioeconomic Index ranges from zero (lowest relative status) to 100 (highest relative status). This measure quantifies disparities in social position of an area's inhabitants and is built from a broad range of demographic, housing, and socioeconomic inputs. More information on this measure can be found in Esri's SEI tutorial.

Mount Airy, MD 21771 - Peer Comparisons by Rank and Percentile

The table below compares 21771 to the other 458 ZIP Codes in Maryland by rank and percentile using July 1, 2025 data. The location Ranked # 1 has the highest value. A location that ranks higher than 75% of its peers would be in the 75th percentile of the peer group.

GROWTH RATE / YEAR	2020-2025	2025-2030
Population	0.42%	0.64%
Households	0.59%	0.71%
Families		0.58%
Median Household Income		2.58%
Per Capita Income		1.94%
Owner Occupied HU		0.87%

Variable Description	Rank	Percentile
Total Population	# 83	82nd
Population Density	# 232	50th
Median Household Income	# 58	88th
Housing Affordability Index	# 377	82nd
Per Capita Income	# 101	78th
Diversity Index	# 289	37th

21771 ZIP Code Profile, Map, Data & Demographics

ZIP Code 21771: Basic Data & USPS Preferred City Name

Mount Airy, MD 21771 Data & Demographics (As of July 1, 2025)

POPULATION

INCOME

HOUSING

HOUSEHOLDS

GROWTH RATE / YEAR

Mount Airy, MD 21771 - Peer Comparisons by Rank and Percentile

Popular Places Near ZIP Code 21771

Use HTL Address Research for a Maryland Address and get...

Quick & Easy Ways to...

Maryland Census Data Comparison Tool

More Tools and Resources:

Frederick County