Great Mills, MD · standard

ZIP Code 20634

St. Mary's County, Maryland — Census ACS demographics, housing tenure, and business patterns, benchmarked against every US ZIP.

Reviewed by PlainZIP Editorial Team, ZIP Code Data Editors · June 13, 2026

5,927
333/sq mi: $139,375
Median income: $342,300
Median home value: 40.3%
Bachelor's or higher

The verdict

Great Mills pairs a top-decile household income with above-median home values, in a low-density, homeowner-dominated area.

Top 5%
household income, US ZIPs: Top 27%
home value, US ZIPs: 333
people per sq mi: 65%
owner-occupied homes

Source: U.S. Census Bureau ACS 5-Year Estimates (2019–2023). Percentiles rank ZIP 20634 against every reporting US ZIP.

ZIP code 20634 is classified by USPS as a standard delivery area and covers roughly 17.8 square miles in Great Mills, St. Mary's County, Maryland. The area is home to 5,927 residents, producing a population density of 333 people per square mile, and falls within the New York time zone. These USPS and Census boundary values drive every downstream statistic on this page, including the benchmarks that compare 20634 against Maryland and the nation.

On the economic side, the median household income for ZIP 20634 sits at $139,375 (22% above the Maryland average), while per-capita income is $61,800. The poverty rate stands at 4.7% and the unemployment rate at 1.3%. On housing, the median home value is $342,300 (24% below the state average) with median rent at $1,814 per month, and 65.4% of occupied units are owner-occupied, a direct signal of whether 20634 behaves more like a homeowner neighborhood or a renter-heavy ZIP.

Education and household profile round out the picture: 40.3% of adults hold a bachelor's degree or higher, the median age is 32, and the average commute is 24 minutes. We also surface 10 nearby ZIP codes within roughly 10 miles and 6 additional ZIPs sharing St. Mary's County, so you can benchmark 20634 against its immediate geography rather than a national average alone. Every figure is sourced from the U.S. Census Bureau American Community Survey 5-Year Estimates, HUD Fair Market Rents, and FHFA Home Price Index data, no estimates, no proprietary scoring. Verify with HUD →

Top industries in ZIP 20634

Construction

11
Retail trade

8
Other services (except public administration)

8
Administrative and support and waste management and remediation services

7
Health care and social assistance

6

What this shows Establishment counts come from the Census ZIP Code Business Patterns program, which counts physical business locations rather than employees or revenue.

Source: U.S. Census Bureau, American Community Survey 5-Year Estimates + ZIP Code Business Patterns + HUD FMR + FHFA HPI ACS demographics, ZBP business establishments, HUD Fair Market Rents, FHFA HPI for ZIP 20634, Great Mills, MD · 2023 Accessed 2026-06-13 Census ACS 5-Year Estimates use a rolling 60-month sample for stable small-geography estimates; ZBP updated annually; HUD FMR + FHFA HPI updated quarterly/annually.

Quick Facts

5,927

Population

17.8

Area (sq mi)

333

People / sq mi

New York

Time Zone

standard

ZIP Type

Neighborhood Scorecard

Get an A-F grade across income, safety, housing, rent, education, commute, and childcare for this ZIP code.

View Scorecard →

Who lives in ZIP 20634?

32.0

Median Age

49.3%

Male

50.7%

Female

6.6%

Foreign-Born

White 56.0%

African American 27.8%

Asian 3.0%

American Indian or Alaska Native 0.0%

Native Hawaiian or Pacific Islander 0.0%

Two or More Ethnicities 9.1%

Hispanic or Latino 8.5%

Hispanic or Latino is an ethnicity category from the Census Bureau and may overlap with other categories above.

Source: U.S. Census Bureau, ACS 5-Year Estimates (2023)

How much do residents earn?

$139,375

Median Household Income

+22% vs state

$61,800

Per Capita Income

4.7%

Poverty Rate

1.3%

Unemployment Rate

23.6 min

Mean Commute Time

How ZIP 20634 ranks nationally

Household income vs. every US ZIP code

Median household income — the full national distribution, with this ZIP marked

$139,375 Top 5% higher than 95% of 30,318 US ZIPs

Each bar is a $20K-wide band; taller bars hold more US ZIPs. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.

Source U.S. Census Bureau — ACS 5-Year Estimates · 2019–2023

Source: U.S. Census Bureau, ACS 5-Year Estimates (2023)

What is the education profile here?

High School Graduate or Higher 59.3%

Bachelor's Degree or Higher 40.3%

Source: U.S. Census Bureau, ACS 5-Year Estimates (2023)

What does housing look like?

3,026

Total Housing Units

2,694

Occupied Units

332

Vacant Units

2.62

Avg Household Size

Occupancy Type

Owner 65.4%

Renter 34.6%

$342,300

Median Home Value

-24% vs state

$1,814

Median Rent

1995

Median Year Built

Source: U.S. Census Bureau, ACS 5-Year Estimates (2023)

How have home values changed over time?

FHFA House Price Index, annual appreciation data based on repeat sales and appraisals

+9.0%

YoY Change (2024)

227

HPI Index (2000 = 100)

+127%

Total Change Since 2000

Home values in ZIP 20634 have increased 9.0% over the past year (2024). Since 2000, this ZIP has seen +127% cumulative appreciation.

Year	Annual Change	HPI Index
2020	-3.2%	172
2021	+8.5%	187
2022	+18.5%	221
2023	-6.0%	208
2024	+9.0%	227

Source: Federal Housing Finance Agency (FHFA) House Price Index, All-Transactions, Five-Digit ZIP Codes (Developmental Index). Index base = 100 in year 2000. Data through 2024. ZIP codes with few transactions may show missing values.

What businesses operate in this ZIP?

Census Bureau data shows 48 business establishments in ZIP 20634, employing approximately 393 people with a combined annual payroll of $19,737,000.

Businesses

393

Employees

$19.7M

Annual Payroll

Industry Sectors

Industry	Establishments	% of Total
Construction	11	22.9%
Retail trade	8	16.7%
Other services (except public administration)	8	16.7%
Administrative and support and waste management and remediation services	7	14.6%
Health care and social assistance	6	12.5%
Real estate and rental and leasing	5	10.4%
Professional, scientific, and technical services	3	6.3%

Source: U.S. Census Bureau, ZIP Code Business Patterns (ZBP), 2023. Employment figures may include noise for disclosure avoidance.

Nearby ZIP Codes

Want a side-by-side? Compare 20634 vs 20620 →

20653

24,481
20619

10,503
20634

5,927
20688

1,828
20620

1,443
20692

1,051
20670

1,014
20674

830
20690

740

What this shows Among its immediate neighbors, ZIP 20634 ranks #3 by population — useful context the national average alone can't give.

20630

$233,411
20692

$201,250
20674

$171,985
20620

$165,972
20634

$139,375
20690

$122,750
20619

$119,432
20653

$103,048
20688

$102,950

What this shows By household income, ZIP 20634 ranks #5 of 9 neighboring ZIPs — local affluence varies block to block, not just metro to metro.

ZIP Code	City	Population	Distance
20620	Callaway, MD	1,443	1.7 mi
20692	Valley Lee, MD	1,051	4.1 mi
20653	Lexington Park, MD	24,481	3.5 mi
20667	Park Hall, MD	494	3.4 mi
20619	California, MD	10,503	3.7 mi
20630	Drayden, MD	348	5.7 mi
20670	Patuxent River, MD	1,014	4.8 mi
20674	Piney Point, MD	830	7.6 mi
20690	Tall Timbers, MD	740	5.9 mi
20688	Solomons, MD	1,828	6.5 mi

More ZIP Codes in St. Mary's County

St. Mary's County Great Mills, MD Maryland

Frequently Asked Questions

What county is ZIP code 20634 in? ▼

ZIP code 20634 (Great Mills) is located in St. Mary's County, Maryland. St. Mary's County contains multiple ZIP codes, see the full list at /counties/st-marys-md.

What is the population of ZIP code 20634? ▼

ZIP code 20634 in Great Mills, MD has a population of 5,927 according to the Census Bureau ACS 2023 estimates.

What is the median household income in ZIP 20634? ▼

The median household income in ZIP 20634 is $139,375, which is 83% above the national average of $76,288.

What is the average home value in ZIP 20634? ▼

The median home value in ZIP 20634 is $342,300, which is 23% above the national average of $278,155.

What is the demographic makeup of ZIP 20634? ▼

The largest racial group in ZIP 20634 is White at 56.0%. Hispanic or Latino residents make up 8.5% of the population.

How many businesses are in ZIP code 20634? ▼

ZIP code 20634 has 48 business establishments employing approximately 393 people, according to Census Bureau ZIP Code Business Patterns (ZBP) 2023 data.

What are the main industries in ZIP code 20634? ▼

The top industries by establishment count in ZIP 20634 are: Construction (11), Retail trade (8), Other services (except public administration) (8). There are 7 industry sectors represented in total.

How have home values changed in ZIP code 20634? ▼

According to the FHFA House Price Index, home values in ZIP 20634 increased by 9.0% in 2024. Since 2000, home values in this ZIP have appreciated by approximately 127%. This is a developmental index based on repeat sales and appraisal data from Fannie Mae and Freddie Mac.

What is the education level in ZIP code 20634? ▼

In ZIP code 20634, 59.3% of residents aged 25+ have a high school diploma or higher, and 40.3% hold a bachelor's degree or higher. These figures come from the Census Bureau ACS 5-Year Estimates (2023).

What is the average commute time in ZIP 20634? ▼

The mean commute time for workers in ZIP code 20634 is 23.6 minutes according to Census ACS data. The national average is roughly 26 minutes, so commuters here spend less time traveling to work than typical.

What percentage of residents own vs. rent in ZIP 20634? ▼

In ZIP code 20634, approximately 65.4% of occupied housing units are owner-occupied and 34.6% are renter-occupied, based on Census ACS 2023 data.

What is the poverty rate in ZIP code 20634? ▼

The poverty rate in ZIP code 20634 is 4.7% according to Census Bureau ACS 2023 estimates. This measures the percentage of the population living below the federal poverty threshold.