| State: | SD |
| Type: | SD |
| Route: | 48 |
| Section: | 168 |
| Map Notes: | Route of SD 48 (in red) |
| Length Mi: | 12.462 |
| Length Ref: | [1] |
| Established: | Circa 1950 |
| Direction A: | West |
| Terminus A: | east of Spink |
| Direction B: | East |
| Terminus B: | Iowa state line west of Akron, Ia. |
| Previous Type: | SD |
| Previous Route: | 47W |
| Next Type: | SD |
| Next Route: | 49 |
South Dakota Highway 48 (SD 48) is a 12.462miles state highway in Union County, South Dakota, United States, that begins at Interstate 29, about 2.5miles west of Spink, and becomes Big Sioux River Road,[2] formerly Iowa Highway 403, northwest of Akron, Iowa.
SD 48 begins at a diamond interchange on I‑29 Exit 31, approximately 44miles south of Sioux Falls.[3] From its western terminus, SD 48 travels due east. It nearly immediately meets County Road 1C (CR 1C), an old alignment of US 77. 2miles east of the CR 1C intersection, SD 48 passes through the town of Spink.
East of Spink, SD 48 gently curves to the north as it descends a rolling hill towards Brule Creek. After crossing the stream, the highway ascends, bending back to the south to resume its due east course. Over the next several miles, the road remains arrow-straight while traversing gently rolling farmland. Just under 10miles east of I‑29, SD 48 serves as the southern terminus of Highway 11 (SD 11). About NaNmiles from the SD 11 junction, SD 48 crosses a bridge over West Union Creek; 1miles later, it crosses East Union Creek.[1] For the remainder of the route, the road gradually S-curves southwest into the Big Sioux River valley. At the Big Sioux River, the road crosses the Iowa state line and ends.
South Dakota 48 was established on a previously unnumbered highway between 1948 and 1953.[4] It began at U.S. Highway 77 (current Union County Road 1C). No significant changes have been made, except for a slight extension to meet Interstate 29 to the west, and a slight realignment at the Iowa border.