Area code 551 is an overlay for area code 201 in northeastern New Jersey, covering cities such as Jersey City, Bayonne, Hoboken, and Englewood. Introduced in 2001, the overlay was necessary to provide additional number availability in one of the most densely populated parts of the United States. Ten-digit dialing is required throughout the 201/551 region. While 201 carries the legacy status, 551 is commonly used for newer phone lines, especially mobile and business numbers. The area is a vital part of the New York metropolitan economy, with robust transportation links and urban development. 551 supports the growth of this dynamic, fast-paced region.