US Map / Regions / Mid-Atlantic
Mid-Atlantic States Map
Officially three states, informally as many as seven. Here is the Census division, the everyday version, and why they disagree.
Which states are in the Mid-Atlantic?
Officially three: New Jersey, New York, and Pennsylvania. That is the Census Bureau's Mid-Atlantic division, and it is much shorter than the list most people have in mind. Between them the three states held about 42.4 million people in 2024 on 99,223 square miles — 428 per square mile, the densest of the nine Census divisions.
| State | Abbr. | Capital | Largest city | Population (2024) | Land area (sq mi) |
|---|---|---|---|---|---|
| New Jersey | NJ | Trenton | Newark | 9,500,851 | 7,354 |
| New York | NY | Albany | New York City | 19,867,248 | 47,126 |
| Pennsylvania | PA | Harrisburg | Philadelphia | 13,078,751 | 44,743 |
New Jersey is the most densely populated state in the country at roughly 1,290 people per square mile; it is also the only one of the three with no Great Lakes frontage. New York and Pennsylvania both reach Lake Erie, and New York's shoreline on Lake Ontario is longer still.
The informal Mid-Atlantic is much bigger
Ask anyone on the east coast and the Mid-Atlantic usually stretches from New York down through Delaware, Maryland, the District of Columbia, and often Virginia and West Virginia. The Census Bureau puts all of those in the South Atlantic division and counts them in the South, a classification inherited from the Mason–Dixon Line rather than from anything about how the area works today. So the honest answer to "which states are Mid-Atlantic" depends on whether you are reading a federal table or a weather map. The regions hub uses the federal version throughout, as this site does.
Cities: the densest urban corridor in the country
New York is the largest city in the United States, about 8.48 million people in 2024 — larger than the second and third cities combined. Philadelphia, about 1.57 million, is sixth nationally. After those two the drop is steep: Newark, Pittsburgh, Jersey City, and Buffalo all sit between roughly 275,000 and 320,000, with Rochester, Syracuse, Allentown, and Albany — the New York state capital — behind them. Almost the entire New Jersey population lives inside the New York or Philadelphia commuting sheds, which is what makes the state's density figure possible.
Geography: a gap in the mountains
The Appalachians cross all three states as the Allegheny Plateau, the Poconos, and the long parallel ridges of the Valley and Ridge province in central Pennsylvania. What matters historically is where they stop: the Hudson–Mohawk corridor through New York is the only sea-level break in the Appalachian chain between Alabama and Canada, and the Erie Canal used it in 1825 to connect New York Harbor to the Great Lakes. That single gap is the reason New York rather than Philadelphia or Baltimore became the country's largest port and city.
The Delaware and Susquehanna rivers drain the middle of the division to the Atlantic; the Susquehanna's mouth is the head of Chesapeake Bay. In the west, Pittsburgh sits where the Allegheny and Monongahela form the Ohio River, so western Pennsylvania's water goes to the Mississippi and the Gulf while the eastern two-thirds of the state drains to the Atlantic coast.
Neighboring divisions
The Mid-Atlantic is the southern half of the Northeast; its sibling is New England. West across the Pennsylvania line is East North Central in the Midwest, and south across the Mason–Dixon Line is South Atlantic in the South. All three states are entirely on Eastern Time.