Claim: Philadelphia is in the Northeast megalopolis.

The Northeast megalopolis -LRB- also Boston -- Washington Corridor or Bos-Wash Corridor -RRB- is the most heavily urbanized region of the United States , running primarily northeast to southwest from the northern suburbs of Boston , Massachusetts , to the southern suburbs of Washington , D.C. , in Northern Virginia . It includes the major cities of Boston , Providence , Hartford , New York City , Philadelphia , Baltimore , and Washington , D.C. , along with their metropolitan areas and suburbs as well as many smaller urban centers .   On a map , the Northeast megalopolis appears almost as a straight line . As of the year 2000 , the region contained 49.6 million people , about 17 % of the U.S. population on less than 2 % of the nation 's land area , with a population density of 931.3 people per square mile -LRB- 359.6 people/km2 -RRB- , compared to the U.S. average of 80.5 per square mile 2 -LRB- 31 people/km2 -RRB- . America 2050 projections expect the area to grow to 58.1 million people by 2025 .   French geographer Jean Gottmann popularized the term in his landmark 1961 study of the region , Megalopolis : The Urbanized Northeastern Seaboard of the United States . Gottmann concluded that the region 's cities , while discrete and independent , are uniquely tied to each other through the intermeshing of their suburban zones , taking on some characteristics of a single , massive city : a megalopolis .