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North American telephone area codes 503 and 971 serve the northwestern region of Oregon, including the Portland, Salem, and Astoria metropolitan areas. ==History== Area code 503 was one of the original area codes created as part of the North American Numbering Plan by AT&T and Bell Laboratories in 1947.〔(【引用サイトリンク】title=Area Code History )〕 Area code 503 was used for the entire state of Oregon until November 5, 1995, when area code 541 began service. With that change, the northwest, and most heavily populated, corner of the state retained the 503 area code and the rest of the state moved to 541. On July 1, 1999, area code 971 was added to share the service area, with the exceptions of Clatsop and Tillamook counties. Initially, 10-digit dialing was to become mandatory in that service area on January 30, 2000, but the date was extended until October 1, 2000. The previously exempted Clatsop and Tillamook counties were added to the 503/971 overlay on April 27, 2008. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Area codes 503 and 971」の詳細全文を読む スポンサード リンク
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