Where is Sullivan County?

6 Sullivan Counties in 6 states · 320,731 people (2025)

There are 6 counties named Sullivan County in the United States, in Indiana, Missouri, New Hampshire, New York, Pennsylvania and Tennessee. The most populous is Sullivan County, Tennessee (county seat: Blountville), with 163,759 people in 2025. 5 of them are named after John Sullivan, American general, politician and judge from New Hampshire (1740-1795).

Map of the United States showing where all 6 Sullivan Counties are, labeled by state
Every Sullivan County in the United States (red), labeled with its state. Boundaries: U.S. Census Bureau, 2025. Free to use with attribution (CC BY 4.0).

All 6 Sullivan Counties

Sorted by state. Each link opens the county's map.

StateCounty seatPopulation 2025Land area (sq mi)EstablishedNamed after
Sullivan County, IndianaSullivan20,8314471816Daniel Sullivan
Sullivan County, MissouriMilan5,7386481843John Sullivan
Sullivan County, New HampshireNewport43,9615381827John Sullivan
Sullivan County, New YorkMonticello80,5869681809John Sullivan
Sullivan County, PennsylvaniaLaporte5,8564501847John Sullivan
Sullivan County, TennesseeBlountville163,7594141779John Sullivan

Questions about Sullivan Counties

How many Sullivan Counties are there?

There are 6 Sullivan Counties in the United States, in Indiana, Missouri, New Hampshire, New York, Pennsylvania and Tennessee.

Which Sullivan County is the largest?

By population, Sullivan County, Tennessee (163,759 people in 2025). By land area, Sullivan County, New York (968 sq mi).

Which Sullivan County is the oldest?

Sullivan County, Tennessee, established in 1779. The newest is Sullivan County, Pennsylvania (1847).

Why are there so many Sullivan Counties?

5 of the 6 are named after John Sullivan, American general, politician and judge from New Hampshire (1740-1795). Many counties took their names from the same founders, presidents and generals as new states were organized.

How do I find out which Sullivan County an address is in?

Open the county map of the state: it has a search box for cities, towns and ZIP codes. On a phone, the "what county am I in" tool on our sister site uses your location.

What county am I in? →

Other common county names