Eastern Seaboard, also called Atlantic Seaboard, region of the eastern United States, fronting the Atlantic Ocean and extending from Maine in the north to Florida in the south. Not merely a geographic term, the Eastern Seaboard is, historically, the part of the United States that was first settled by European immigrants and from which most westward American settlement originated. In popular usage, the Eastern Seaboard connotes the coastal settlements from Boston to Philadelphia, an area of heavy urbanization, in which are islands of great poverty and conspicuous wealth, business and financial centres, major educational institutions, and a high level of social and cultural sophistication.