Area Code 201

201 is a New Jersey area code, covering most of Hudson and Bergen counties, and parts of Essex and Passaic counties. It is overlaid with area code 551. Until 1958, 201 was the only area code for the entire state of New Jersey, and has the distinction of being the first North American area code. With the overlay of the 551 area code, 10-digit dialing is now mandatory in New Jersey.