Delaware Counties by Population (2026)

There are 3 counties in Delaware.

New Castle County is the largest county in the state, with a population of 599,629. The most recent census shows that its population has increased by 0.05% 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 : 285,452
• Kent County : 197,824

Delaware Counties with the Fewest Residents

The smallest county in Delaware is Kent County , with a population of just 197,824. This total represents a increase of 0.1% since the last census count was performed.

Other small counties include:

• Sussex County : 285,452
• New Castle County : 599,629

Delaware Counties with Rapid Growth

Sussex County , with its sizeable population of 285,452, 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 0.05% with 599,629 residents.