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🇺🇸 United States ZIP Code

PO BOX

21920

Elk Mills

ZIP Code 21920 is a po box zip code serving Elk Mills, Elk Mills, Maryland (MD), in Cecil County, United States. It has an estimated population of 257 with a median household income of $31,833. The area falls within the America/New_York timezone.

Median Household Income vs. National Average

$0 National: $37,585 $150K+ $31,833

Location

Country
🇺🇸 United States
State / Province
Maryland (MD)
County
Cecil
City
Elk Mills
Timezone
America/New_York

Coordinates

Latitude
39.658000
Longitude
-75.828200

Geographic Details

Land Area
0.50 mi²
Population Density
516.0 people per mi² (70th percentile)
Bounding Box
39.664625°N, 39.649374°S, -75.820137°E, -75.836311°W

With 257 residents spread across 0.50 square miles, this area has a population density of 516.0 people per square mile.

Demographics

257

Population

5th percentile

$31,833

Median Income

10th percentile

$285,400

Median Home Value

85th percentile

0.50 mi²

Land Area

The median household income in 21920 is $31,833, and the median home value is $285,400. This is below the national average for household income.

Housing

100

Total Units

92

Occupied Units

92.0%

Occupancy Rate

Similar ZIP Codes in Maryland

ZIP codes with similar median household income in Maryland.

21201

Baltimore

$27,465

 21202

Baltimore

$30,425

 21213

Baltimore

$34,046

 21215

Baltimore

$34,471

 21216

Baltimore

$31,988

 21531

Friendsville

$36,831

 21541

Mc Henry

$32,415

 21817

Crisfield

$31,522

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.