| 600 | Special telecommunications needs in Canada |
| 601 | Mississippi (Jackson, Meridian, Natchez, McComb, Hattiesburg and central Mississippi, overlays with 769) |
| 602 | Arizona (Central Phoenix only) |
| 603 | New Hampshire (all) |
| 604 | British Columbia (Greater Vancouver Regional District and Abbotsford overlay with 778. Whistler, Chilliwack and remaining portion of 604 not part of overlay complex). The whole area, along with area code 250 will overlay with area code 778 in 2008 |
| 605 | South Dakota (all) |
| 606 | Kentucky (Ashland, Hazard, Somerset, London, Corbin, Pikeville, Maysville and eastern Kentucky) |
| 607 | New York (Binghamton, Elmira, Bath, Norwich, Oneonta, Ithaca, and south central New York) |
| 608 | Wisconsin (Madison, La Crosse, Platteville, Beloit and southwestern Wisconsin) |
| 609 | New Jersey (Atlantic City, Brown Mills, Trenton, and central & southeastern New Jersey) |
| 610 | Pennsylvania (Reading, Chester and southeastern Pennsylvania, overlays with 484 and 835) |
| 611 | Repair Service |
| 612 | Minnesota (Central Minneapolis, Fort Snelling, St Anthony and Richfield) |
| 613 | Ontario (Ottawa, eastern and southeastern Ontario) |
| 614 | Ohio (Columbus area) |
| 615 | Tennessee (Nashville, Murfreesboro, Springfield, Lebanon, Dickson and north central Tennessee), split from 901 in 1954. |
| 616 | Michigan (Grand Rapids, Holland, Greenville, Grand Haven, Zeeland, Ionia and southwestern Michigan) |
| 617 | Massachusetts (Boston, Cambridge, east central Massachusetts and close-in Boston suburbs, overlays with 857) |
| 618 | Illinois (Alton, Belleville, Carbondale, Centralia, Mount Vernon and southern Illinois) |
| 619 | California (Southern and eastern suburbs and southern portion of the city of San Diego) Former area code for areas now covered by 858 and 760 |
| 620 | Kansas (Dodge City, Great Bend, Parsons, Liberal and southern Kansas not including the Wichita metropolitan area) |
| 623 | Arizona (Glendale, Buckeye, Peoria, western Phoenix area and western Phoenix suburbs only) |
| 626 | California (Arcadia, Temple City, Covina, Pasadena and eastern Los Angeles suburbs) |
| 627 | California This Area code is scheduled to provide numbering relief to Area code 707 but no date has been assigned for this to go into effect. |
| 628 | California This Area code is scheduled to provide numbering relief to Area code 415 but no date has been assigned for this to go into effect. |
| 630 | Illinois (Aurora, Naperville, and other Western Chicago suburbs, overlays with 331) |
| 631 | New York (Suffolk County)-had previously been under 516. |
| 636 | Missouri (St. Charles, Chesterfield, Union, De Soto, Troy and east central Missouri) |
| 641 | Iowa (Mason City, Oskaloosa, Creston, Pella, Ottumwa, Britt, Clear Lake, Fairfield and central Iowa) |
| 646 | New York (New York City: Manhattan only; cell phone overlays with 212 and 917) |
| 647 | Ontario (Toronto; overlays with 416) |
| 649 | the Turks and Caicos Islands, split from Area code 809. (all) |
| 650 | California (San Mateo, Palo Alto, Redwood City, Menlo Park, Mountain View and southern San Francisco suburbs) |
| 651 | Minnesota (St Paul, Lindstrom, Red Wing, Hastings and east central Minnesota) |
| 657 | California This Area code is scheduled to provide numbering relief to Area code 714 with a planned in service date of September 23, 2008. |
| 659 | Alabama This Area code is scheduled to provide numbering relief to Area code 205 but no date has been assigned for this to go into effect. |
| 660 | Missouri (Marshall, Sedalia, Macon, Trenton, Maryville, Bethany and north central Missouri) |
| 661 | California (Bakersfield, Mojave, Santa Clarita, Palmdale and south central California) |
| 662 | Mississippi (Greenville, Tupelo, Winona, Columbus, Holly Springs and northern Mississippi) |
| 664 | Montserrat, split from 809. (all) |
| 667 | Maryland This Area code is scheduled to provide numbering relief to Area code 443 but no date has been assigned for this to go into effect. |
| 669 | California This Area code is scheduled to provide numbering relief to Area code 408 but no date has been assigned for this to go into effect. |
| 670 | Northern Marianas (former country code for this territory of the United States) |
| 671 | Guam (former country code for this territory of the United States) |
| 678 | Georgia (all of metro Atlanta, overlays both 404 and 770 and in the future 470) |
| 679 | Michigan This Area code is scheduled to provide numbering relief to Area code 313 but no date has been assigned for this to go into effect. |
| 681 | West Virginia (taking full effect in 2009; overlay of 304) |
| 682 | Texas (Fort Worth, Arlington, Grandview, Weatherford, Rhome, overlays with 817) |
| 684 | American Samoa (former country code for this territory of the United States) |
| 689 | Florida This Area code is scheduled to provide numbering relief to Area code 407 but no date has been assigned for this to go into effect. |
