Area codes 314 and 557 are telephone area codes in the North American Numbering Plan (NANP) in the U.S. state of Missouri, serving the city of St. Louis and most of its inner-ring suburbs in neighboring St. Louis County. The numbering plan area is bordered to the west by area code 636, which serves St. Louis' outer suburbs to the west, south, and north. Across the Mississippi River to the east, 314 is adjacent to area code 618, which serves southern Illinois and most of Metro East. Area code 557 was added to the 314 numbering plan area on August 12, 2022, to form an overlay numbering plan.
Area codes 920 and 274 are telephone area codes in the North American Numbering Plan (NANP) for a large area of eastern Wisconsin. Area code 920 was created on July 26, 1997, in a split of area code 414, one of the original North American area codes of 1947. 274 was added to the same numbering plan area (NPA) on May 5, 2023 to create an area code overlay.
Area code 564 is a telephone overlay area code in the North American Numbering Plan (NANP) for Western Washington state, including metropolitan Seattle. The area code was first proposed in 1999 to relieve telephone number shortages in area code 360, but implementation was delayed until 2017, when it was installed for an overlay complex that comprises only the numbering plan area 360. Neighboring area codes 206, 253, and 425 were slated for expansion of the overlay upon exhaustion of central office codes in each NPA. In 2023, area code 206 was approved for expansion with a guide line for preparation of inclusion of at least nine months. Ten-digit dialing has been mandatory in all of western Washington since July 29, 2017.
Area codes 909 and 840 are telephone area codes in the North American Numbering Plan for the far-eastern part of Los Angeles County and southwestern San Bernardino County in the U.S. state of California. Area code 909 was created on November 14, 1992, in an area code split of 714, and 840 was added to the numbering plan area to form an overlay complex effective February 23, 2021.
Area codes 516 and 363 are telephone overlay area codes in the North American Numbering Plan (NANP) for the U.S. state of New York. The numbering plan area (NPA) comprises Nassau County on Long Island. Area code 516 was created in 1951 and 363 was added to the numbering plan area in 2023.
Area code 404 is a telephone area code in the North American Numbering Plan (NANP) for Atlanta, Georgia and its closest suburbs. This comprises roughly the area encircled by Interstate 285. It is an enclave area code, surrounded by area code 770, which serves most of Atlanta's suburbs. Both 404 and 770 are overlaid by area codes 678, 470, and 943.
Area codes 202 and 771 are telephone area codes in the North American Numbering Plan (NANP) for Washington, D.C.
Area codes 608 and 353 are telephone area codes in the North American Numbering Plan for much of southwestern Wisconsin, including the state capital city Madison. Area code 608 was assigned in 1955 to a numbering plan area created from areas with area code 414 and area code 715, and was the third area code created in Wisconsin. Rapid growth of the area, specifically in Dane County, brought the area code close to exhaustion of central office prefixes, with NANPA projections in 2022 projecting the need for relief by late 2023. In September 2022, the Wisconsin Public Service Commission and North American Numbering Plan Administrator (NANPA) announced an overlay complex for the numbering plan area with new area code 353, with an in-service date of September 15, 2023. New central office code orders were accepted starting on July 11, 2023, but activatlon is contingent on complete exhaustion of central office codes for 608.
Area codes 813 and 656 are area codes in the North American Numbering Plan for the U.S. state of Florida in the city of Tampa, Florida, and its surrounding areas, such as Zephyrhills and Oldsmar. In 2022, due to exhaustion of central office prefixes, area code 656 was added to the service area forming an overlay complex.
Area codes 717 and 223 are telephone area codes in the North American Numbering Plan (NANP) for South Central Pennsylvania and the Susquehanna Valley. The numbering plan area (NPA) includes the Harrisburg, Lancaster, and York metropolitan areas and a considerable portion of Pennsylvania Dutch Country, an area with nearly two million people.
Area codes 610, 484, and 835 are telephone area codes in the North American Numbering Plan (NANP) for the eastern and southeastern regions of Pennsylvania. The numbering plan area (NPA) includes regions to the west of Philadelphia and the cities Allentown, Bethlehem, and Reading. It includes much of the Delaware Valley, including almost all of Delaware County, most of the Philadelphia Main Line, and all of the Lehigh Valley.
Area codes 215, 267, and 445 are telephone area codes in the North American Numbering Plan (NANP) for Philadelphia and adjacent portions of Bucks and Montgomery counties in the U.S. state of Pennsylvania. Area code 215 was one of the original North American area codes established in 1947, while 267 and 445 are overlay codes for the same numbering plan area (NPA).
Area codes 301, 240, and 227 are telephone area codes in the North American Numbering Plan (NANP) for the western part of the U.S. state of Maryland. The numbering plan area (NPA) comprises Maryland's portion of the Greater Washington, D.C. metro area, portions of southern Maryland, along with rural western Maryland. This includes the communities of Cumberland, Frederick, Hagerstown, Gaithersburg, Potomac, Germantown, Bethesda, Rockville, Landover, Silver Spring, and Waldorf.
Area codes 814 and 582 are telephone area codes in the North American Numbering Plan (NANP) for the northwestern and central portions of the Commonwealth of Pennsylvania. Cities served by the area code include Altoona, Bradford, DuBois, Erie, Meadville, Oil City, Titusville, Johnstown, St. Marys, and Warren as well as the boroughs of State College, Brockway, Clearfield, Huntingdon, Mount Union, Bedford, Clarion, Punxsutawney, Tyrone, Ebensburg, Coudersport, Ridgway and Brookville. Area code 814 is the original area code assigned to the numbering plan area in 1947. Area code 582 was activated in the service area as an additional code to form an overlay numbering plan with a starting date of October 3, 2020.
Area code 412 is a telephone area code in the North American Numbering Plan (NANP) for the Commonwealth of Pennsylvania. The numbering plan area (NPA) comprises the city of Pittsburgh, most of surrounding Allegheny County, and small portions of Washington and Westmoreland counties. The area code was one of the original North American area codes created in 1947, when it was assigned to the entire southwestern corner of the state. On August 17, 2001, the numbering plan area was converted to an overlay complex with area code 878, which also forms an overlay with area code 724, in the surroundings of the 412 service area.
Area codes 210 and 726 are telephone area codes in the North American Numbering Plan (NANP) for the San Antonio area in the U.S. state of Texas. Area code 210 was created in an area code split from number plan area 512 in 1992. After only a few years, the threat of number exhaustion forced a reduction of the size of the numbering plan area to the center of the San Antonio metropolitan area in 1997. Area code 726 was assigned to the same numbering plan area in an overlay complex activated in 2017 to alleviate the threat of exhaustion of central office codes that was expected by 2018. Area codes 210 and 726 are enclave codes for an area completely surrounded by numbering plan area 830.
Area code 878 is an area code in the North American Numbering Plan for Southwestern Pennsylvania, centered in Pittsburgh. It forms an overlay complex with two distinct numbering plan areas, 412 in Pittsburgh and some suburban areas and 724 in surrounding 412 in the southwestern corner of the state. Area code 878 was activated on August 17, 2001.
Area codes 513 and 283 are telephone area codes in the North American Numbering Plan (NANP) for the southwest of the U.S. state of Ohio, including Cincinnati and surrounding cities, such as Forest Park, Hamilton, Lebanon, West Chester, Mason, Maineville, Middletown, Milford, Norwood, Oxford, Harrison, Cleves, Miamitown and Trenton.
Area codes 816 and 975 are telephone area codes in the North American Numbering Plan (NANP) for most of the Missouri side of the Kansas City metropolitan area, the St. Joseph area, and all or part of 15 surrounding counties in northwestern Missouri. The numbering plan area originally comprised most of the northern and western two-thirds of the state, bordering with Arkansas, Illinois, Iowa, Kansas, Nebraska, and Oklahoma, but has been reduced to a ribbon bordering Kansas. 816 is one of the original 86 area codes created in 1947. The numbering plan area was converted to an overlay complex with area code 975 in 2023.
Area code 423 is a telephone area code in the North American Numbering Plan for the U.S. state of Tennessee. It comprises two disconnected areas of East Tennessee that are separated by area code 865.
