EAS 506,436,,,Available,,Available outside Madawaska: Maine EAS 506,728,,,Available,,Available outside Madawaska: Maine EAS A few towns and suburbs on US state boundaries have one central office which serves both sides, using different prefixes in different area codes. All South Coffeyville, Oklahoma exchange prefixes are served from Coffeyville, Kansas, population 10000; the two are local to each other but long distance to everything else. The towns of Seekonk and Rehoboth, Massachusetts share a wire center with East Providence, Rhode Island and code protection was provided in the 401 area code until 2000, allowing Seekonk and Rehoboth subscribers (336-xxxx) to dial calls in the Providence, Rhode Island metro area with 7 digits. This was phased out when New England Telephone began the process of creating an overlay area code for the 508 area code. Ten-digit dialing is now required for calls crossing the area code (and state) boundary. Limitations If code protection is implemented by reserving every seven-digit number for a border town in both (or all) of the affected area codes, that community and points in its local calling area occupy numbering resources at double the otherwise-expected rate. This is a minor drawback in small cities with large rural area codes (as the numbers can easily be assignable in distant locations), but can consume numbers rapidly in larger centers such as St. Louis or Kansas City (where such protection must be maintained throughout most or all of the area code region, reducing its lifespan). In large cities located directly on area code boundaries (such as Ottawa-Hull in 613/819, the sixth-largest Canadian metropolitan area), this can lead to a situation where none of the many vacant prefixes can be assigned without breaking seven-digit calling across the area code boundary. Code protection in Ottawa-Hull broke down in 2006 for this reason. The 1-819 versions of Ottawa 1-613 numbers could not be assigned anywhere in western Quebec, even to areas a safe distance from the National Capital Region, such as the Eastern Townships or northwestern Quebec. Eventually, the few remaining prefixes in area code 819 could not be assigned without requiring ten-digit dialing from Ottawa to Hull. A local calling area spanning three American or Canadian jurisdictions would require any number local to any part of the town to be reserved across all three (or more) area codes. This ultimately led to the breakdown of seven-digit calling between Washington, D.C. and its suburbs in 1991. Since