South Dakota has 1 active area code serving the entire state across two time zones. The 605 area code covers all communities from Sioux Falls to Rapid City, making South Dakota one of only 11 states that still uses a single area code.
Whether you need to identify an unknown caller, plan business communications across the Central and Mountain time zones, or schedule calls to different regions of the state, this guide provides complete and current information about South Dakota’s telecommunications system.
Key Takeaways:
- South Dakota uses only one area code (605) for the entire state, making it one of 11 US states with a single area code
- Area code 605 was established in 1947 as one of the original 86 area codes in the North American Numbering Plan
- The state spans two time zones: Central Time (eastern portion including Sioux Falls) and Mountain Time (western portion including Rapid City)
- No overlays or splits have ever occurred in South Dakota due to the state’s low population density (approximately 886,000 residents)
- The area code covers 66 counties and 273 cities, serving both urban centers and rural communities
South Dakota Area Code
| Area Code | Primary Cities/Regions | Time Zone | Type | Year Introduced |
|---|---|---|---|---|
| 605 | Sioux Falls, Rapid City, Aberdeen, Brookings, Watertown, Pierre, Mitchell, Yankton, Huron, Vermillion | Central Time (CT) / Mountain Time (MT) | Original | 1947 |
Area Code 605: Statewide Coverage
Area code 605 was established on January 1, 1947, as one of the original 86 area codes in the North American Numbering Plan. The middle digit “0” indicated that 605 covered an entire state, a convention used until 1953. This area code has served South Dakota continuously for over 75 years without splits or overlays.
Geographic Coverage and Major Cities
The 605 area code covers all 66 counties across South Dakota’s 77,116 square miles. Major cities include Sioux Falls (the state’s financial and healthcare hub), Rapid City (gateway to the Black Hills and Mount Rushmore), Aberdeen, Brookings (home to South Dakota State University), Watertown, Pierre (state capital), Mitchell, Yankton, Huron, and Vermillion.
The state’s economy is grounded in agriculture, financial services, healthcare, and tourism, with the Black Hills region drawing millions of visitors annually.
Current Status and Future Outlook
The 605 area code serves approximately 886,000 residents with 731 active prefixes (71% landlines, 29% wireless). Despite 93% of prefixes being assigned, the area code is not currently in jeopardy of exhaustion. However, projections from 2023 suggest relief action may be needed by late 2026, likely through an overlay that would preserve existing 605 numbers while adding a new area code to the same region.
Understanding Time Zones in South Dakota
South Dakota spans two time zones despite having one area code. Eastern South Dakota, including Sioux Falls, follows Central Time (UTC-6 standard, UTC-5 daylight). Western South Dakota, including Rapid City and the Black Hills, observes Mountain Time (UTC-7 standard, UTC-6 daylight).
The division roughly follows the Missouri River. Both regions observe daylight saving time, with clocks changing on the second Sunday in March and first Sunday in November.
Scheduling Considerations
When calling within South Dakota, remember the one-hour time difference. A 9:00 AM call from Central Time reaches Mountain Time at 8:00 AM. Always confirm the recipient’s time zone before scheduling important calls or meetings between eastern and western South Dakota.
South Dakota Cities and Their Area Code
| City | Area Code | Time Zone | Notable Information |
|---|---|---|---|
| Sioux Falls | 605 | Central Time | Largest city, population ~195,000, financial hub |
| Rapid City | 605 | Mountain Time | Second-largest city, gateway to Black Hills |
| Aberdeen | 605 | Central Time | Third-largest city, regional hub for northeastern SD |
| Brookings | 605 | Central Time | Home to South Dakota State University |
| Watertown | 605 | Central Time | Fourth-largest city, near Minnesota border |
| Pierre | 605 | Central Time | State capital, population ~14,000 |
| Mitchell | 605 | Central Time | Home of the Corn Palace |
| Yankton | 605 | Central Time | Historic river town on Missouri River |
| Huron | 605 | Central Time | Geographic center of South Dakota |
| Vermillion | 605 | Central Time | Home to University of South Dakota |
| Spearfish | 605 | Mountain Time | Northern Black Hills community |
| Brandon | 605 | Central Time | Fast-growing suburb of Sioux Falls |
| Box Elder | 605 | Mountain Time | Adjacent to Ellsworth Air Force Base |
| Sturgis | 605 | Mountain Time | Famous for annual motorcycle rally |
| Belle Fourche | 605 | Mountain Time | Geographic center of the United States |
How to Use Area Codes in South Dakota
Dialing Requirements
Since October 24, 2021, all calls within South Dakota require ten-digit dialing (605 + seven-digit number), even for local calls. This change was implemented nationwide to accommodate 988 as the National Suicide Prevention Lifeline. Both mobile and landline numbers use the same format with no distinction in dialing procedures.
Calling South Dakota
From within the US or Canada, dial 1-605-XXX-XXXX for long-distance calls.
International callers should use +1-605-XXX-XXXX. Number portability allows users to transfer numbers between carriers, and approximately 29% of prefixes are now designated for wireless use.
Will South Dakota get a new area code soon?
Projections from 2023 suggest South Dakota may need relief action by late 2026. If required, it would likely be an overlay, adding a second area code to the same geographic region while preserving existing 605 numbers.
Is 605 a toll-free number?
No, 605 is a geographic area code, not toll-free. Calls may incur long-distance charges depending on your plan. Toll-free numbers use prefixes like 800, 888, 877, 866, 855, 844, and 833.