Delaware county geography overview
Delaware has 3 counties, which places it 50th among the 50 state and District of Columbia maps in this atlas when ordered by number of county-level units. Their combined 1,948.5 square miles of land place the state 49th by mapped land area.
The average county-level area is 650 square miles, while the median is 586.1 square miles. The median is often the better description of a typical unit because one or two very large areas can pull the average upward. The five largest units together account for about 100% of the state’s mapped land area.
Largest and smallest Delaware counties
Sussex County is the largest county-level unit by land area at 936.1 square miles. It represents about 48% of all mapped land in Delaware. At the other end of the range, New Castle County has 426.3 square miles of land.
Largest by land area
- Sussex County936.1 sq mi
- Kent County586.1 sq mi
- New Castle County426.3 sq mi
Smallest by land area
- New Castle County426.3 sq mi
- Kent County586.1 sq mi
- Sussex County936.1 sq mi
Rankings use land area rather than total area. This avoids making coastal or lake counties appear larger solely because their boundaries include extensive water.
Alphabetical list of Delaware counties
The table is alphabetical, so it works as a name and FIPS-code reference rather than an area ranking. Every identifier begins with the Delaware state FIPS prefix 10. Land and water figures are rounded to one decimal place.
3 county-level areas
Download county data / numbered map key (CSV)| No. | Name | FIPS code | Land area | Water area |
|---|---|---|---|---|
| 1 | Kent County | 10001 | 586.1 sq mi | 212.3 sq mi |
| 2 | New Castle County | 10003 | 426.3 sq mi | 67.7 sq mi |
| 3 | Sussex County | 10005 | 936.1 sq mi | 260.3 sq mi |
How to read and use this map
County lines are administrative boundaries, not postal routes. A mailing address can use a city name associated with a neighboring area, and ZIP codes can cross county lines. When you need to identify a county for an address, confirm it with an official geocoder or local government source.
For classroom or planning use, download a PDF from the controls above. Labelled exports use numbered callouts for crowded areas; numbered quiz maps match the alphabetical county list. SVG files keep the boundary lines sharp at larger paper sizes.
Interpreting the water figure: About 22% of the summed mapped area in this state is water. County water area can include coastal waters, bays, lakes, or rivers assigned by the Census boundary file; it is shown separately from land and should not be used to estimate developable land.
Frequently asked questions
How many counties are in Delaware?
Delaware has 3 counties in the U.S. Census Bureau’s 2025 cartographic boundary file.
Can I print this Delaware county map?
Yes. Choose Download / print and select PDF for a landscape Letter page, PNG for an image, or SVG for editable vector artwork. Because the map is SVG, its boundary lines stay sharp when scaled.
What is the largest county in Delaware?
Sussex County is the largest by land area in this dataset at 936.1 square miles. This is an area ranking, not a population ranking.
What is the smallest county in Delaware?
New Castle County is the smallest by land area in this dataset at 426.3 square miles.
Are these legal survey boundaries?
No. This is a generalized reference map. Property, parcel, election, and legal boundary questions should be checked with the relevant state or local agency.
Map source
U.S. Census Bureau, 2025 Cartographic Boundary File, Counties, 1:5,000,000. Land and water area fields are supplied in the same file and converted from square meters to square miles. Accessed September 27, 2026.