🇺🇸 United States ZIP Code

STANDARD

21758

Knoxville

ZIP Code 21758 is a standard zip code serving Knoxville, Knoxville, Maryland (MD), in Frederick County, United States. It has an estimated population of 4,921 with a median household income of $88,274. The area falls within the America/New_York timezone.

Median Household Income vs. National Average

Location

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

Coordinates

Latitude: 39.347900
Longitude: -77.651300

Geographic Details

Land Area: 32.43 mi²
Water Area: 2.43 mi²
Population Density: 152.0 people per mi² (55th percentile)
Bounding Box: 39.415398°N, 39.303516°S, -77.563003°E, -77.761010°W

With 4,921 residents spread across 32.43 square miles, this area has a population density of 152.0 people per square mile.

Demographics

4,921

Population

55th percentile

$88,274

Median Income

90th percentile

$258,700

Median Home Value

80th percentile

32.43 mi²

Land Area

The median household income in 21758 is $88,274, and the median home value is $258,700. This places the area in the top 25% nationally for household income.

Housing

1,882

Total Units

1,749

Occupied Units

92.9%

Occupancy Rate

Similar ZIP Codes in Maryland

ZIP codes with similar median household income in Maryland.

20842

Dickerson

$78,608

21733

Fairplay

$82,778

20622

Charlotte Hall

$98,750

21162

White Marsh

$80,341

21403

Annapolis

$83,056

21713

Boonsboro

$76,412

21154

Street

$76,548

20650

Leonardtown

$99,936

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.