Where is Union County?

17 Union Counties in 17 states · 1.2 million people (2025)

There are 17 counties named Union County in the United States, in Arkansas, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Mississippi, New Jersey, New Mexico, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, South Dakota and Tennessee. The most populous is Union County, New Jersey (county seat: Elizabeth), with 601,863 people in 2025. 4 of them are named after United States, country located primarily in North America.

Map of the United States showing where all 17 Union Counties are, labeled by state
Every Union 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 17 Union Counties

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

StateCounty seatPopulation 2025Land area (sq mi)EstablishedNamed after
Union County, ArkansasEl Dorado36,9261,0391829–
Union County, FloridaLake Butler16,2502441921–
Union County, GeorgiaBlairsville27,8593241832–
Union County, IllinoisJonesboro16,6564131818United States
Union County, IndianaLiberty6,8631611821union
Union County, IowaCreston11,8294241851United States
Union County, KentuckyMorganfield12,8393431811–
Union County, MississippiNew Albany28,4594161870–
Union County, New JerseyElizabeth601,8631031857Union
Union County, New MexicoClayton3,8443,8251894–
Union County, North CarolinaMonroe267,6746331842merger
Union County, OhioMarysville73,4464321820–
Union County, OregonLa Grande25,9002,0371864Union
Union County, PennsylvaniaLewisburg42,3133161813United States
Union County, South CarolinaUnion26,7995141798–
Union County, South DakotaElk Point17,4024621862United States
Union County, TennesseeMaynardville21,4502241850–

Questions about Union Counties

How many Union Counties are there?

There are 17 Union Counties in the United States, in Arkansas, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Mississippi, New Jersey, New Mexico, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, South Dakota and Tennessee.

Which Union County is the largest?

By population, Union County, New Jersey (601,863 people in 2025). By land area, Union County, New Mexico (3,825 sq mi).

Which Union County is the oldest?

Union County, South Carolina, established in 1798. The newest is Union County, Florida (1921).

Why are there so many Union Counties?

4 of the 17 are named after United States, country located primarily in North America. Many counties took their names from the same founders, presidents and generals as new states were organized.

How do I find out which Union 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