THE MERCER COUNTY LAND BRIEF
Land in the
Triassic Lowlands setting.
Mercer County has 224.5 square miles of land in New Jersey. 4 mapped landscape regions meet across Mercer County: Triassic Lowlands, Inner Coastal Plain, Trap Rock and Conglomerate Uplands, among others.
Rounded low hills, open valleys and irregular plains form a transition between Appalachian highlands and the coastal plain. The underlying geology mixes metamorphic, igneous and sedimentary rocks.
Regional context: Northern Piedmont ↗ · Regional mapping across the county footprint
Where the landscape changes
Mercer County intersects 4 mapped regional units. The largest mapped shares are:
- Triassic Lowlands46.6%
- Inner Coastal Plain45.3%
- Trap Rock and Conglomerate Uplands5.9%
- Delaware River Terraces and Uplands2.2%
Atlantic Coastal Pine Barrens in Mercer County
Sandy coastal landscapes combine beaches, dunes, bays and marshes with oak-pine woodland. These pine-barrens settings form a transition between warmer southern coasts and rockier shores farther north.
Read the regional source ↗Middle Atlantic Coastal Plain in Mercer County
Low coastal plains contain terraces, estuaries, marshes and barrier islands. Unconsolidated sediments underlie this varied coastal setting, with forest patterns changing near streams and low-lying areas.
Read the regional source ↗Finding your parcel within Mercer County
The atlas lists 25 cities, towns, townships, and Census communities associated with Mercer County, including Hopewell, Hamilton, West Windsor. The list includes overlapping geography types and does not divide the county into exclusive service areas.
Mercer County by land and water
The Census records 4.37 square miles of water within Mercer County, or 1.9% of its total area. That share is close to Mercer County’s 1.9%. This is geographic context; waterfront status and usable land must be checked at the parcel.
For scale, Mercer County has 10.3 times the land area of nearby Lawrence township (21.7 square miles). These areas describe boundaries, not comparable property prices.
The Census boundary meets Burlington County, Hunterdon County, Middlesex County, Monmouth County, Somerset County within New Jersey. A tract near one of these lines should be matched to the county identifier on its own records.

