Area code 605

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Area code 605 is the telephone area code in the North American Numbering Plan (NANP) for the entire U.S. state of South Dakota. The numbering plan area was designated in 1947, when the American Telephone and Telegraph Company (AT&T) devised a comprehensive telephone numbering plan for the United States and Canada.

Before October 2021, area code 605 had telephone numbers assigned for the central office code 988. In 2020, 988 was designated nationwide as a dialing code for the National Suicide Prevention Lifeline, which created a conflict for exchanges that permit seven-digit dialing. Area code 605 was therefore scheduled to transition to ten-digit dialing by October 24, 2021.^[1]

Projections of 2023 suggest that South Dakota's numbering plan area will require relief action to avoid exhaustion of central office prefixes by late 2026,^[2]

The numbering plan area includes the following communities, which are serviced by the listed central office prefixes.

• List of North American Numbering Plan area codes
• Original North American area codes

• "Area Code Maps". North American Numbering Plan Administrator.