201 area code is a New Jersey (United States of America) telephone area code. It covers counties of Bergen and Hudson, and partly Passaic and Essex. This area code is the last one assigned in the U.S.A. plan of North American numbering (North American Numbering Plan). This plan includes twenty-four territorial units: the USA territories, Bermuda, Caribbean territories (sixteen of them) and Canada. Although the name of the plan suggests the northern American areas, it doesn’t really include all of them.
Although it was planned to be assigned in 1947, 201 was assigned in 1951. The first call to be made using this area code was from New Jersey (Englewood) to California (Alameda). From that time to 1958, 201 was the only New Jersey area code. In 1958 New Jersey got another area code – 609, so that was when 201 stopped being the only area code used in the state of New Jersey. 201 remained in usage for the northern parts: Bergen, Union, Hudson, Essex, Passaic, Middlesex, Morris, Somerset, Warren, Sussex and Monmouth; the southern parts (suburban areas of Delaware, Wilmington and Philadelphia) started using 609.
During the 1990s, some of the counties have stopped to use 201 and started to use the new area code – 973. Those counties were Passaic, Morris, Essex and Sussex. The counties that have continued to use 201 were Bergen and Hudson. However, these two counties kept growing in population, so 201 was not sufficient. The question was whether to split it or to add an overlay code. The final decision was to add another overlaying area code, since this option was less expensive and simpler. But in 2001 the obligation to use ten-digit dialing led to creation of more overlay area codes. Those were area codes 551, 862 and 848 (overlaying 973 and 732).