Area code 810
Cities covered 
- Grand Blanc
- Marine City
- Mount Morris
- Port Huron
- St. Clair
- Swartz Creek
- selected areas in north Oakland County areas of Oxford, Addison, Brandon, Groveland, and Holly are also partially served by 810.
When it was implemented on December 1, 1993, 810 was Michigan's first new area code since 1961 and received much fanfare. It originally served all suburbs of Detroit north of Wayne County and communities farther north that were formerly served by 313.
Only four years later, Oakland County was split off as area code 248. This led to a situation in which residents of southwest Macomb County could leave their area code area by traveling one or two miles westwards, but reenter it by continuing west for another 30 miles.
In the early 21st century, when area code 586, including most of Macomb County, was split off from 810, only the northern communities of Macomb and Oakland counties remained served by 810.
Prior usage for TWX 
The 810 area code (along with area codes 510, 610, 710, and 910) was used prior to 1981 by AT&T for their TWX, or TeletypeWriter eXchange network. The area code was decommissioned for TWX usage in 1981 when Western Union, who had acquired the TWX network in 1969 from AT&T and renamed it Telex II, upgraded the network to "4-row" ASCII operation (it previously used both "3-row" Baudot and ASCII transmission).
See also 
|Michigan area codes: 231, 248, 269, 313, 517, 586, 616, 734, 810, 906, 947, 989|
|West: 517, 989||area code 810||East: 519/226, Lake Huron|
|South: 734, 248/947, 586|
|Ontario area codes: 226, 249, 289, 343, 365, 416, 519, 613, 647, 705, 807, 905|
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