Philadelphia English or Delaware Valley English is a variety or dialect of American English native to Philadelphia and extending into Philadelphia's metropolitan area throughout the Delaware Valley, including southeastern Pennsylvania, all of South Jersey, counties of northern Delaware (especially New Castle and Kent), and the northern Eastern Shore of Maryland. Aside from Philadelphia and the surrounding counties and arguably Baltimore, the dialect is spoken in places such as Reading, Camden, Atlantic City, Wilmington, Vineland, and Dover. Philadelphia English is one of the best-studied types of English, as Philadelphia's University of Pennsylvania is the home institution of pioneering sociolinguist William Labov. Philadelphia English shares certain features with New York City English and Midland American English, although it remains a distinct dialect of its own. Philadelphia and Baltimore accents together fall under what Labov describes as a single Mid-Atlantic regional dialect.
According to linguist Barbara Johnstone, migration patterns and geography affected the dialect's development, which was especially influenced by immigrants from Northern England, Scotland, and Northern Ireland.[citation needed] Today, an especially marked or "heavier" Philadelphia accent is most commonly found in Irish-American and Italian-American working-class neighborhoods, though the accent is prominent and pervasive to varying degrees throughout the entire Delaware Valley among all socioeconomic levels.