🇺🇸 United States ZIP Code

PO BOX

21664

Secretary

ZIP Code 21664 is a po box zip code serving Secretary, Secretary, Maryland (MD), in Dorchester County, United States. It has an estimated population of 539 with a median household income of $52,604. The area falls within the America/New_York timezone.

Median Household Income vs. National Average

Location

Country: 🇺🇸 United States
State / Province: Maryland (MD)
County: Dorchester
City: Secretary
Timezone: America/New_York

Coordinates

Latitude: 38.609300
Longitude: -75.947400

Geographic Details

Land Area: 0.43 mi²
Water Area: 0.03 mi²
Population Density: 1245.0 people per mi² (80th percentile)
Bounding Box: 38.613891°N, 38.600917°S, -75.935966°E, -75.953544°W

With 539 residents spread across 0.43 square miles, this area has a population density of 1245.0 people per square mile.

Demographics

539

Population

15th percentile

$52,604

Median Income

60th percentile

$154,400

Median Home Value

60th percentile

0.43 mi²

Land Area

The median household income in 21664 is $52,604, and the median home value is $154,400.

Housing

236

Total Units

215

Occupied Units

91.1%

Occupancy Rate

Similar ZIP Codes in Maryland

ZIP codes with similar median household income in Maryland.

20609

Avenue

$53,203

20722

Brentwood

$56,133

20737

Riverdale

$59,427

20743

Capitol Heights

$57,973

20755

Fort George G Meade

$58,643

20770

Greenbelt

$59,857

20782

Hyattsville

$59,574

20783

Hyattsville

$57,787

Frequently Asked Questions

What information is available for each ZIP code?

Each ZIP code page shows city, state, county, geographic coordinates, timezone, population, median household income, median home value, housing units, land area, population density, commute time, educational attainment, area codes, and ZIP code type (Standard, PO Box, or Unique).

What are the different types of ZIP codes?

There are three types of ZIP codes: Standard (residential and commercial delivery areas), PO Box (assigned to post office box sections), and Unique (assigned to a single high-volume address like a government agency or large company). Standard ZIP codes are the most common.

How often is ZIP code data updated?

ZIP code assignments are updated quarterly by the USPS. Demographic data comes from the US Census Bureau's American Community Survey (ACS), which releases new 5-year estimates annually. ZipFYI updates its data to reflect the latest available information.

What is population density and why does it matter?

Population density measures the number of people per square mile in a ZIP code area. It helps identify urban vs. rural areas, affects real estate values, impacts service availability, and is used in market analysis. Dense urban ZIP codes may have 50,000+ people per square mile.

How are ZIP code boundaries determined?

ZIP code boundaries are determined by the USPS based on mail delivery routes, not political or geographic boundaries. They follow carrier routes and may cross city, county, or even state lines. Boundaries can change when the USPS reorganizes delivery operations.

What does median household income tell me about a ZIP code?

Median household income is the middle value when all household incomes in a ZIP code are sorted. Half of households earn more and half earn less. It is a better indicator of typical earnings than average income, which can be skewed by very high or very low outliers.