County · code 34021
Mercer CountyNew Jersey
Mercer County is in New Jersey with its county seat in Trenton. It was formed on February 22, 1838, from parts of Burlington, Hunterdon, and Middlesex counties, and named after Hugh Mercer.
- Founded1838
- County seatTrenton
- Named forHugh Mercer
- Land area224 sq mi + 4.4 sq mi water
- Population387,340 2020 Census
- Parcels mapped142,341 checked 15 October 2026
Where it is
Mercer 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 1838 from Burlington County, Hunterdon County and Middlesex County
An old deed may name a county that no longer exists, or a boundary that has since moved.
Mercer County was created on February 22, 1838, from Burlington, Hunterdon, and Middlesex counties. Just five days later, on February 27, 1838, Mercer gained territory from Somerset County. Over the following years, the county exchanged land with Hunterdon County through gains in 1839 and 1845 and a loss in 1844.
- 1838Mercer County created Mercer created from Burlington, Hunterdon, and Middlesex. · N.J. Acts 1838, p. 99; Snyder, 37
- 1838Gained territory Mercer gained from Somerset. · N.J. Acts 1838, pp. 209-210; Snyder, 37
- 1839
- 1844
- 1845
Land and parcels
What the maps cover in Mercer
Who publishes each layer, how good it is, and when we last checked.
-
Parcels Good enough
Lot lines and tax-map numbers for 142,341 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, 150,013 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
Mercer by the Census
Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.
Rules and offices
Mercer 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 Mercer County.
See your own lot on these maps
Open Mercer 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.
Questions
Common questions about Mercer County
- When was Mercer County founded?
- Mercer County was founded in 1838, formed from Burlington County, Hunterdon County and Middlesex County, and named after Hugh Mercer.
- What is the county seat of Mercer County?
- The county seat of Mercer County is Trenton.
- Is there an online parcel map for Mercer County?
- Yes. A public source publishes a parcel map of 142,341 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
- Has Mercer County's boundary or name changed?
- Mercer County was created in 1838 from Burlington County, Hunterdon County and Middlesex County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Hunterdon County and Somerset County.
- Is my lot in a flood zone?
- We do not have flood maps for Mercer County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.
Nearby