313 Area Code – Detroit, Michigan: Location, Time Zone & History

One of the original 86 North American area codes assigned in October 1947, 313 originally covered all of southeastern Michigan, including Metro Detroit, Flint, and the southern Thumb region, before two later splits narrowed its footprint to Detroit and its closest Wayne County suburbs.

The northern portion of the territory split off in 1993 to form area code 810, and the western portion followed in 1997 as area code 734, taking Ann Arbor, Monroe County, and the downriver suburbs. Those two divisions left the numbering plan area limited to Detroit, Dearborn, Hamtramck, Grosse Pointe, and Lincoln Park, a footprint that has held largely steady since, even as the local economy shifted from automotive manufacturing alone toward mobility technology, healthcare, and higher education.

Detroit's identity is closely bound to Motown Records, founded in the city in 1959, and the code itself has become cultural shorthand—commemorated each March 13 as "313 Day," a local holiday formally established by a Detroit City Council resolution in 2022. Growth pressures continued into the next decade: the Michigan Public Service Commission announced the 679 overlay in March 2025, with new numbers entering service that November after a period of mandatory ten-digit dialing.