Delaware Counties by Population (2025)

There are 3 counties in Delaware.

New Castle County is the largest county in the state, with a population of 585,268. The most recent census shows that its population has increased by 0.03% since the previous census.

A number of other Delaware counties also boast relatively large populations for their state, though not able to match the density of New Castle County:

• Sussex County : 277,633
• Kent County : 193,851

Delaware Counties with the Fewest Residents

The smallest county in Delaware is Kent County, with a population of just 193,851. This total represents a increase of 0.1% since the last census count was performed.

Other small counties include:

• Sussex County : 277,633
• New Castle County : 585,268

Delaware Counties with Rapid Growth

Sussex County, with its sizeable population of 277,633, has shown the largest population growth, with an increase of 0.2% since the last census.

New Castle County has also had relatively high population growth of 0.03% with 585,268 residents.