Area code 231

231 is a North American telephone area code in the U.S. state of Michigan. Area Code 231 includes the Northwestern part of Michigan's Lower peninsula. Areas included are Muskegon, Petoskey, Ludington, Baldwin, Traverse City, and Pentwater. It was created in June 1999 as a split from area code 616. 231 is essentially the northern half of the old 616 area code. 616 previously covered the entire western half of the state of Michigan, extending west from the north-south line aligned with the Mackinac Bridge.

Area Code 231 serves all of Northwestern Lower Michigan. It extends all the way from Muskegon in the Southern portion of the area code to Petoskey in the far North. Similar to many other area codes, 231 has small irregularities. While the Southern border is exactly along county boundaries the eastern border is rigid. Appearing at first to end at the Peirson area of Montcalm county, the border takes an awkward curve to the east several times to avoid area code 989 from dominating the entirety of Michigan.

Among the Michigan cities it serves are Big Rapids, Cadillac, Grant, Kalkaska, Ludington, Manistee, Muskegon, Petoskey, Newaygo, and Traverse City.

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