the Washington local access and transport area (LATA) spills into portions of Maryland and Virginia, every number in the area that was in Maryland's area code 301 and northern Virginia's area code 703 was given a "hidden" number in the District's area code 202. However, this meant that if a central office code was in use in any portion of the metro area, it could not be used even in areas a safe distance from Washington such as southwestern Virginia or the Eastern Shore of Maryland. Severing the border community from its exhausted home area code using a split plan may prolong the life of a seven-digit exchange code protection scheme if the piece being split off is outside the extended local calling area. Code protection is most often removed entirely in large cities if an overlay plan is implemented, as these plans break the seven-digit dialling that code protection was devised to preserve. The plan also can be expected to break down if new split-plan codes are added within a city the size of Chicago, as the city itself no longer fits into one seven-digit area. See also Linked numbering scheme Area code 202 and 301/703, Washington DC and MD/VA Area code 314/618, St. Louis/East St. Louis Area code 613/819, Ottawa-Hull Area code 712/605/402, Sioux City metropolitan area (three states) Area code 816/913, Kansas City Notes References North American Numbering Plan