Atlantic City formed on May 1, 1854, in advance of the rail line opening on July 4 of that year.

[17] With more people moving to the area in the late 1800s into the early 1900s, several municipalities were created in short succession – Margate City (then called South Atlantic City) in 1885, Somers Point in 1886, Pleasantville and Linwood in 1889, Brigantine in 1890, Longport in 1898, Ventnor in 1903, Northfield and Port Republic in 1905, and Folsom in 1906.

[17][24] In 1973, the New Jersey Coastal Area Facilities Review Act required additional state permitting for construction in the eastern half of the county.

[17] In the same ballot as the 1976 presidential election, 56.8% of New Jersey voters approved an initiative to allow legalized gambling in Atlantic City.

Hard Rock Hotel & Casino Atlantic City opened in 2018, refurbishing the former Trump Taj Mahal.

[28][22] Beneath the county is a mile of clay and sand that contains the Kirkwood–Cohansey aquifer, which supplies fresh groundwater for all of the streams and rivers in the region.

The interior of the county is part of the Pine Barrens, which covers the southern third of New Jersey, and is prone to forest fires.

[31] In December 1992, a nor'easter produced the highest tide on record in Atlantic City, 9.0 ft (2.7 m) above mean lower low water.

[32] Former Hurricane Sandy struck near Brigantine as an extratropical cyclone, which produced an all-time minimum barometric pressure of 948.5 mbar (28.01 inHg) and wind gusts to 91 mph (146 km/h) in Atlantic City, as well as a storm surge that inundated low-lying areas.

[38] As of 2025[update], Atlantic County Executive is Dennis Levinson (R, Northfield), whose four-year term of office ends December 31, 2027.

[39] Members of the Board of County Commissioners are (with terms for chair and vice-chair ending December 31):[36][40][37] Democrats have not won a county-wide office since 2020.

[61][62] For the 119th United States Congress, New Jersey's 2nd congressional district is represented by Jeff Van Drew (R, Dennis Township).

The county flipped to Donald Trump in 2024, having previously not voted for a Republican presidential candidate since George H. W. Bush in 1988.

It is considered a swing county in down-ballot races, and Republicans hold most of its seats in the state legislature and in county-level offices.

[66][67] The Bureau of Economic Analysis calculated that the county's gross domestic product was $12.4 billion in 2021, which was ranked 15th in the state and was an 8.8% increase from the prior year.

The first railroad across the county opened in 1854, intended to assist the bog iron industry; instead, it spurred development in Atlantic City, as well as the growth of farming towns.

During the prohibition era, the winery obtained a government permit to sell wine tonic for medicinal purposes.

Balic Winery opened in 1966 in Mays Landing,[76] although its vineyards date back to the early 19th century.

[82] In 2015, Tuckahoe Brewing moved from Ocean View to a facility in Egg Harbor Township capable of producing four times the amount of beer.

[95] In 1928, Dr. Charles Ernst and Dr. Frank Inksetter built Atlantic Shores Hospital and Sanitarium in Somers Point as a private institute for the treatment of alcohol and drug dependency.

In 1940, citizens turned the facility into the not-for-profit Shore Medical Center, which has expanded over time to add more beds and units.

[21][98] The indigenous people of New Jersey developed a series of trails across the state, including one from current-day Absecon to Camden.

An early coastal road was constructed in 1716 from Somers Point to Nacote Creek in Port Republic.

Roads into the county's interior were slow, unreliable, and muddy, with one main roadway along the Mullica River that eventually connected to Burlington.

[24] A notable railroad tragedy occurred on October 28, 1906, when three train cars derailed on a draw bridge into 30 ft (9.1 m) deep water in Beach Thorofare, killing 53 people, with only two survivors.

[24] In the late 1800s, a bridge opened in Mays Landing, providing road access to the county's interior.

[24] Amid pressure from motorists and cyclists, the county improved the conditions of the roads in the early 20th century.

[104] The Great Egg Harbor Bridge opened in 1956, marking the completion of the Garden State Parkway, which connected Cape May and Atlantic counties, continuing to North Jersey.

[105] As early as 1990, the South Jersey Transportation Authority had plans to construct an Atlantic County Beltway as a limited-access road, beginning along Ocean Heights Avenue in southern Egg Harbor Township at a proposed Exit 32 with the Garden State Parkway.

The proposed road would pass west of the Atlantic City Airport and reconnect with the Parkway at Exit 44 via County Route 575 in Galloway Township.