605 area code — Sioux Falls, SD geographic

Data: NANPA public reports, current as of July 28, 2026.

The 605 area code covers Sioux Falls, South Dakota, Central and Mountain time zone, and dates back to January 1, 1947. Note that porting and VoIP mean a 605 number can be used from anywhere — the code marks where the number was assigned.

742 central-office prefixes are currently active in this code, spread across 92 code-holding carriers. Thousands-block pooling applies to 363 prefixes, so a single prefix can belong to several carriers. Its prefixes map to 269 distinct rate centers.

Unusually, 605 spans two time zones (Central and Mountain). When returning a call, check which part of South Dakota the prefix belongs to — the difference is a full hour.

Dialing: 10D locally, 10D to other codes (1+10 digit permissible at service provider discretion.).

Worth noting: 605 is the only area code serving South Dakota; it is also one of the few NANP area codes whose territory spans two time zones.

Practical takeaway: the 605 label narrows geography to South Dakota, the prefix narrows it to a locality, and neither authenticates a caller. Verification means calling back through a number you found yourself.

NANPA projects numbering capacity to exhaust in 3Q 2034.

Largest localities in 605

FAQ

Will 605 run out of numbers?

NANPA's current forecast projects exhaust in 3Q 2034 — decades of capacity remain.

Why am I getting spam calls from 605 numbers?

Scammers spoof recognizable area codes so calls look local or familiar. A displayed 605 number does not prove the call originated there — see our guide to spotting spoofed calls.

Where is a 605 number from?

605 is assigned to Sioux Falls and surrounding areas of South Dakota in the Central and Mountain time zone. The three digits after the area code (the prefix) narrow it down to a rate center.

Is 605 a toll-free number?

No. 605 is a geographic code; calls are billed like any other domestic call. Toll-free codes are 800, 833, 844, 855, 866, 877 and 888.