When was Union County founded?

Union County was founded in 1857, formed from Essex County, and named after Union.

What is the county seat of Union County?

The county seat of Union County is Elizabeth.

Is there an online parcel map for Union County?

Yes. A public source publishes a parcel map of 149,454 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Union County's boundary or name changed?

Union County was created in 1857 from Essex County. Since then the Atlas of Historical County Boundaries records 5 later changes, most of them small boundary adjustments, chiefly involving Essex County, Middlesex County and Somerset County.

Is my lot in a flood zone?

We do not have flood maps for Union County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Union County, New Jersey: parcels, history and offices

Where it is

Union on the map of New Jersey

New Jersey has 21 counties and county equivalents, each with its own records office. Shapes with a page are links.

History

Formed in 1857 from Essex County

An old deed may name a county that no longer exists, or a boundary that has since moved.

Union County was created from Essex County on March 19, 1857, and was named after Union. The county gained territory from Middlesex County in 1860, and exchanged small areas with Middlesex, Somerset, and Essex counties over the following decades.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries; the 5 that matter most are shown first.

1857
Union County created Union created from Essex.
from Essex
19 March 1857 · N.J. Acts 1857, pp. 244-245; Snyder, 41
1860
Gained territory Union gained from Middlesex.
from Middlesex
16 February 1860 · N.J. Acts 1860, p. 97; Snyder, 42
1871
Lost territory Union lost small area to Middlesex.
to Middlesex
5 April 1871 · N.J. Acts 1871, pp. 1255-1256; Snyder, 42
1891
Gained territory Union gained small area from Essex.
from Essex
17 February 1891 · N.J. Acts 1891, p, 536; Snyder, 43-44
1958
Lost territory Union lost small area on the line between Millburn and Springfield townships to Essex.
to Essex
29 July 1958 · N.J. Acts 1958, pp. 630-632; Snyder, 47-48

Show all 11 changes (6 more, mostly small adjustments)

1857
Union County created Union created from Essex.
from Essex
19 March 1857 · N.J. Acts 1857, pp. 244-245; Snyder, 41
1860
Gained territory Union gained from Middlesex.
from Middlesex
16 February 1860 · N.J. Acts 1860, p. 97; Snyder, 42
1871
Boundary clarified Boundary between Union and Essex clarified (no change).
with Essexno change
21 March 1871 · N.J. Acts 1871, p. 604; Snyder, 42
1871
Lost territory Union lost small area to Middlesex.
to Middlesex
5 April 1871 · N.J. Acts 1871, pp. 1255-1256; Snyder, 42
1876
Boundary clarified Boundary between Union and Essex redefined (no change).
with Essexno change
22 February 1876 · N.J. Acts 1876, p. 482; Snyder, 42
1876
Changed Boundary between Union and Somerset adjusted to follow small change in Green Brook.
Somerset
16 March 1876 · N.J. Acts 1876, pp. 484-485; Snyder, 42-43
1882
Boundary clarified Boundary between Union and Essex clarified (no change).
with Essexno change
17 March 1882 · N.J. Acts 1882, pp. 365-366; Snyder, 43
1891
Gained territory Union gained small area from Essex.
from Essex
17 February 1891 · N.J. Acts 1891, p, 536; Snyder, 43-44
1892
Boundary clarified Boundary between Union and Essex redefined (no change).
with Essexno change
3 February 1892 · N.J. Acts 1892, pp. 483-484; Snyder, 44
1892
Boundary clarified Water boundaries of Union, Bergen, Hudson, Middlesex, and Monmouth redefined to match the New Jersey-New York interstate boundary agreement of 1834, as detailed by joint commissions in 1887 and 1889.
with Bergen with Hudson with Middlesex with Monmouthno change
9 April 1892 · N.J. Acts 1892, p. 441; Snyder, 44-45
1958
Lost territory Union lost small area on the line between Millburn and Springfield townships to Essex.
to Essex
29 July 1958 · N.J. Acts 1958, pp. 630-632; Snyder, 47-48

Land and parcels

What the maps cover in Union

Who publishes each layer, how good it is, and when we last checked.

Parcels Good enough

Lot lines and tax-map numbers for 149,454 parcels. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 15 October 2026
Address points Official

One point per address, 231,012 in all from NJOGIS.
edited 23 September 2026 · checked 14 October 2026
Buildings Reference

Roof outlines traced from aerial imagery from FEMA Response Geospatial Office with Oak Ridge National Laboratory (ORNL). Good for seeing what is on a lot; not accurate enough to set a fence from.
checked 18 October 2026

Official: from the office that keeps the record
Good enough: a reliable statewide or national copy
Fallback: a guide only; check the official record
Missing: nothing public found yet

People and land

Union by the Census

Population

575,345 2020 Census count

Housing units

209,908 2020 Census count

Land area

103 square miles

Water area

2.6 square miles

People per sq mi

5,598 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Union County's official site

We have found the county's site but not its offices yet; start there.

County government

County government
The official website of Union County.
ucnj.org

See your own lot on these maps

Open Union County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.

Open the free map no sign-in Pro early access

Questions

Common questions about Union County

When was Union County founded?: Union County was founded in 1857, formed from Essex County, and named after Union.
What is the county seat of Union County?: The county seat of Union County is Elizabeth.
Is there an online parcel map for Union County?: Yes. A public source publishes a parcel map of 149,454 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Union County's boundary or name changed?: Union County was created in 1857 from Essex County. Since then the Atlas of Historical County Boundaries records 5 later changes, most of them small boundary adjustments, chiefly involving Essex County, Middlesex County and Somerset County.
Is my lot in a flood zone?: We do not have flood maps for Union County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby

Union CountyNew Jersey