Simply put, "313" is the area code for Detroit. Residents of Southeastern Michigan might remember when this area code was enough to handle all of the public switched telephone network for Wayne, Washtenaw, Macomb and Oakland counties. The area code has been split numerous times in recent years, to where Detroit is now virtually synonomous with the numbers "313." Convenient for our purposes at least ...

Here's how the area codes in Michigan are currently broken down: