When was Somerset County founded?

Somerset County was founded in 1688, and named after Somerset, England.

What is the county seat of Somerset County?

The county seat of Somerset County is Somerville.

Is there an online parcel map for Somerset County?

Yes. Somerset County publishes a parcel map of 132,895 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Somerset County's boundary or name changed?

Somerset County was created in 1688. Since then the Atlas of Historical County Boundaries records 12 later changes, chiefly involving Middlesex County, Hunterdon County and Essex County.

Is my lot in a flood zone?

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

County · code 34035

Somerset CountyNew Jersey

Somerset County is a county in New Jersey with its seat in Somerville, formed in 1688.

Founded1688
County seatSomerville
Named forSomerset, England
Land area302 sq mi + 3.1 sq mi water
Population345,361 2020 Census
Parcels mapped132,895 checked 15 October 2026

Open the free map Click any parcel in Somerset County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated 19 October 2026

Census outline · seat marked

History

Founded in 1688

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

Somerset County was created in 1688 from Middlesex County in East New Jersey, though it was not fully organized and remained attached to Middlesex. The county was fully organized and detached from Middlesex in 1714, after a series of boundary adjustments with neighboring counties.

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

1688
Somerset County created Somerset was created in East New Jersey from Middlesex; not fully organized, attached to Middlesex.
from Middlesex
14 May 1688 · Leaming and Spicer, 305; Snyder, 12, 29
1688
Lost territory Somerset lost to Non-County Area (West) in West New Jersey when the absentee governors of East and West New Jersey agreed on a compromise boundary between the two colonies that ran irregularly from the northern end of the Keith Line (1687) to the land boundary with New York. 5 September 1688 · Snyder, 9, 31
1710
Gained territory 21 January 1709/1710. Somerset gained from Middlesex.
from Middlesex
21 January 1710 · Paterson, 2-3; Snyder, 30-32
1714
Lost territory 15 March 1713/1714. Somerset lost to Middlesex.
to Middlesex
15 March 1714 · Paterson, 4-5; Snyder, 32
1741
Gained territory Somerset gained from Essex.
from Essex
4 November 1741 · Paterson, 13; Snyder, 32

Show all 17 changes (12 more, mostly small adjustments)

1688
Somerset County created Somerset was created in East New Jersey from Middlesex; not fully organized, attached to Middlesex.
from Middlesex
14 May 1688 · Leaming and Spicer, 305; Snyder, 12, 29
1688
Lost territory Somerset lost to Non-County Area (West) in West New Jersey when the absentee governors of East and West New Jersey agreed on a compromise boundary between the two colonies that ran irregularly from the northern end of the Keith Line (1687) to the land boundary with New York. 5 September 1688 · Snyder, 9, 31
1710
Gained territory 21 January 1709/1710. Somerset gained from Middlesex.
from Middlesex
21 January 1710 · Paterson, 2-3; Snyder, 30-32
1714
Lost territory 15 March 1713/1714. Somerset lost to Middlesex.
to Middlesex
15 March 1714 · Paterson, 4-5; Snyder, 32
1714
Changed In 1714, Somerset was fully organized, detached from Middlesex.
Middlesex
31 December 1714 · Snell, 568
1741
Gained territory Somerset gained from Essex.
from Essex
4 November 1741 · Paterson, 13; Snyder, 32
1749
Boundary clarified Boundary between Somerset and Morris redefined (no change).
with Morrisno change
28 March 1749 · Paterson, 14; Snyder, 34
1790
Boundary clarified Boundary between Somerset and Middlesex clarified (no change).
with Middlesexno change
24 November 1790 · Paterson, 103; Snyder, 34
1838
Lost territory Somerset lost to Mercer.
to Mercer
27 February 1838 · N.J. Acts 1838, pp. 209-210; Snyder, 37
1844
Gained territory Somerset gained from Hunterdon.
from Hunterdon
13 March 1844 · N.J. Acts 1844, p. 253; Snyder, 38
1845
Lost territory Somerset lost to Hunterdon.
to Hunterdon
14 February 1845 · N.J. Acts 1845, p. 45; Snyder, 38
1850
Lost territory Somerset lost to Middlesex.
to Middlesex
1 February 1850 · N.J. Acts 1850, pp. 5-6; Snyder, 40
1855
Gained territory Somerset gained small areas from Middlesex along road between Kingston and New Brunswick.
from Middlesex
29 March 1855 · N.J. Acts 1855, pp. 490-491; Snyder, 40-41, 169, 175
1858
Exchanged territory Somerset exchanged small areas with Middlesex along road between Kingston and New Brunswick.
with Middlesex
6 February 1858 · N.J. Acts 1858, p. 29; Snyder, 42, 169, 175, 221, 227
1876
Changed Boundary between Somerset and Union adjusted to follow small change in Green Brook.
Union
16 March 1876 · N.J. Acts 1876, pp. 484-485; Snyder, 42-43
1878
Boundary clarified Boundary between Somerset and Middlesex redefined (no change).
with Middlesexno change
29 March 1878 · N.J. Acts 1878, pp. 568-569; Snyder, 43
1965
Boundary clarified Boundary between Somerset and Hunterdon clarified (no change).
with Hunterdonno change
17 December 1965 · N.J. Acts 1965, p. 861; Snyder, 48

Land and parcels

What the maps cover in Somerset

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

Parcels Good enough

Lot lines and tax-map numbers for 132,895 parcels from Somerset County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
edited 16 September 2026 · checked 15 October 2026
Address points Official

One point per address, 137,166 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

Somerset by the Census

Population

345,361 2020 Census count

Housing units

131,822 2020 Census count

Land area

302 square miles

Water area

3.1 square miles

People per sq mi

1,144 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

Somerset 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 Somerset County.
co.somerset.nj.us

See your own lot on these maps

Open Somerset 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 Somerset County

When was Somerset County founded?: Somerset County was founded in 1688, and named after Somerset, England.
What is the county seat of Somerset County?: The county seat of Somerset County is Somerville.
Is there an online parcel map for Somerset County?: Yes. Somerset County publishes a parcel map of 132,895 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Somerset County's boundary or name changed?: Somerset County was created in 1688. Since then the Atlas of Historical County Boundaries records 12 later changes, chiefly involving Middlesex County, Hunterdon County and Essex County.
Is my lot in a flood zone?: We do not have flood maps for Somerset County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby