Area code 203 is a North American telephone area code that is assigned to the southwestern part of Connecticut, and is overlaid with area code 475. The numbering plan area (NPA) 203 originally covered the entire state of Connecticut when the North American Numbering Plan was created in 1947. Today the numbering plan area stretches from Connecticut's western border, along its southern coast, to Madison, and north to Meriden. The region encompassed by 203 and 475 is mostly coextensive with the Connecticut side of the New York metropolitan area.
The counties included in numbering plan area 203/475 are:
Cities and towns served by 203/475:
The city of Meriden is notable as the only place in Connecticut from where one can call towns in either the Hartford or New Haven exchanges toll-free from a landline telephone.
The Connecticut Department of Public Utility Control, in August 1999, proposed an area code overlay for the 203 area code. Area code 475 went into effect on December 12, 2009. Even though area code 475 overlays only 203, all callers in Connecticut (including those in area code 860) had to dial all calls with ten digits, effective November 14, 2009; this was in preparation for the overlay of area code 959 on area code 860 that was implemented in 2014.
The first range of available numbers made available in Connecticut's third area code was (475) 882-4xxx, in the Huntington section of Shelton.