605 Area Code: Sioux Falls, South Dakota

South Dakota is served by a single area code, 605, which covers the entire state. Sioux Falls, on the Big Sioux River, anchors the directory's records here. The city sits at the falls that give it its name — a short stretch of cascades cut into the Sioux Quartzite — organized around a downtown that has reshaped itself substantially over the past two decades alongside a substantial healthcare sector (Sanford Health and Avera Health both maintain large operations) and a long-running role as the regional commercial center for an unusually large share of the northern Plains. The 605 footprint takes in Rapid City (the gateway to the Black Hills), Aberdeen, Pierre (the state capital), and the rest of the state.

Because 605 covers South Dakota entirely, the directory's records associated with 605 numbers do not surface a recurring set of out-of-state cities through the routine cross-linkage patterns that dominate larger codes. Where other-place names do appear, they reflect the same kinds of public-record dynamics seen elsewhere — numbers porting between carriers, addresses tied to multiple residences, and prior registrations surfacing alongside current ones. The directory currently documents 455 distinct prefixes within 605 in detail, a working subset of the prefix population the code actually carries.

Sioux Falls's home values come in close to the US median, with median household income running below the national figure but not severely so. The city's median age sits a few years under the US reading, and population places Sioux Falls as the largest city in South Dakota — substantial in its regional context, smaller in the broader US frame.