As of the 2020 census, the county was the state's 15th-most-populous county with a population of 274,534. Its county seat is the Mays Landing section of Hamilton Township.

The most populous place in Atlantic County was Egg Harbor Township, with 47,842 residents as of the 2020 census. Galloway Township, covering 115.21 square miles, has the largest total area of any municipality, though Hamilton Township has the largest land area, covering 111.13 square miles.

Cape May County is the southernmost county in the state, with much of the county is located on the Cape May peninsula, bound by the Delaware Bay to its west and the Atlantic Ocean to its south and east.

Adjacent to the Atlantic coastline are five barrier islands that have been built up as seaside resorts. A consistently popular summer destination with 30 miles of beaches, Cape May County attracts vacationers from New Jersey and surrounding states, with the summer population exceeding 750,000.

Tourism is the county's single largest industry and the associated leisure and hospitality industries are Cape May's largest employers. Its county seat is the Cape May Court House section of Middle Township. As of the 2020 census, the county was the state's second-least populous county with a population of 95,263.

As of the 2020 census, the county is the state's 16th-most-populous county with a population of 154,152. Its county seat is Bridgeton. Cumberland County is named for Prince William, Duke of Cumberland and was formally created from portions of Salem County in 1748.

The most populous municipality is Vineland, with a 2020 population of 60,780. The largest municipality by area is Maurice River Township, covering 95.76 square miles.

Salem County is the westernmost county in the state of New Jersey. Its western boundary is formed by the Delaware River and  the Delaware Memorial Bridge connects the county with New Castle, DE. Its county seat is Salem.

As of the 2020 census, the county retained its position as the state's least-populous county with a population of 64,837. The most populous place in Salem County is Pennsville Township with 12,684 residents as of the 2020 Census. Lower Alloways Creek Township covers 72.46 square miles, the largest total area of any municipality.