Area code 313

Area code 313 is an area code within the North American Numbering Plan serving Detroit and most of its closest suburbs in Wayne County, Michigan. It includes the enclave cities Hamtramck and Highland Park, as well as Dearborn, Dearborn Heights, Inkster, Melvindale, the Grosse Pointe communities, Lincoln Park, Redford, and Taylor north of Goddard Road, River Rouge, and Ecorse.

The Numbering Plan Area 313 was created as one of the original 86 plan areas in 1947. It included the entire southeastern quadrant of Michigan, including Metro Detroit, Flint, and the southern part of Michigan's "Thumb." The original boundaries were such that Jackson and everything surrounding it in present day 517 was included in 313, while Flint and many communities surrounding it were in 517. A realignment in the 1950s resulted in these two cities swapping codes.

Because of the demand for new telephone service, area code 810 was created for the northern suburbs, Flint, and the "southern" Thumb on December 1, 1993. On December 13, 1997, the 313 area was further divided, creating the 734 area out of Washtenaw County, Monroe County, plus western and downriver Wayne County.

...
Wikipedia