# U.S. Route 18 in South Dakota

U.S. Highway 18 (US 18) is a part of the United States Numbered Highway System that travels from Orin, Wyoming, to Milwaukee, Wisconsin. In the state of South Dakota, US 18 runs from the Wyoming border east to the Iowa border. The highway runs parallel to the state's southern border with Nebraska, and at one point, near Fairfax, US 18 comes within one mile to the Nebraska border.

## Route description

US 18 enters South Dakota west of Edgemont. It passes through Hot Springs, the Pine Ridge Indian Reservation, the Rosebud Indian Reservation, Winner, and Gregory, before crossing the Missouri River near Pickstown over Fort Randall Dam. East of the Missouri River, US 18 passes through (or near) Lake Andes and Tripp before a brief concurrency with Interstate 29 (I-29) near Worthing. East of I-29, US 18 passes through Canton before crossing the Big Sioux River into Iowa.
The South Dakota section of US 18 is legally defined at South Dakota Codified Laws § 31-4-141.

## Major intersections

| County | Location | mi | km | Destinations | Notes |
| Fall River | ​ | 0.00 | 0.00 | US 18 west – Lusk | Continuation into Wyoming |
| Fall River | Edgemont | 12.10 | 19.47 | SD 471 south – Edgemont, Provo | Northern terminus of SD 471 |
| Fall River | ​ | 24.18 | 38.91 | SD 89 north – Custer | Southern terminus of SD 89 |
| Fall River | Hot Springs | 39.82 | 64.08 | SD 71 south – Ardmore | Northern terminus of SD 71 |
| Fall River | Hot Springs | 40.54 | 65.24 | US 385 north – Mount Rushmore, Wind Cave National Park | Western end of US 385 concurrency |
| Fall River | Maverick Junction | 44.67 | 71.89 | SD 79 north – Rapid City | Western end of SD 79 concurrency |
| Fall River | Oelrichs | 62.27 | 100.21 | US 385 south / SD 79 south – Chadron | Eastern end of US 385/SD 79 concurrency |
| Oglala Lakota | Pine Ridge | 103.53 | 166.62 | SD 407 south – Rushville | Northern terminus of SD 407 |
| Oglala Lakota | ​ | 120.99 | 194.71 | SD 391 south – Gordon | Northern terminus of SD 391 |
| Bennett | Martin | 148.94 | 239.70 | SD 73 south – Merriman | Western end of SD 73 concurrency |
| Bennett | ​ | 161.42 | 259.78 | SD 73 north – Kadoka | Eastern end of SD 73 concurrency |
| Todd | ​ | 189.98 | 305.74 | SD 63 north – Parmelee, Norris | Southern end of SD 63 |
| Todd | ​ | 206.35 | 332.09 | US 83 north – White River | Western end of US 83 concurrency |
| Todd | Mission | 209.69 | 337.46 | US 83 south – Valentine | Eastern end of US 83 concurrency |
| Tripp | ​ | 242.54 | 390.33 | SD 53 south – Clearfield | Western end of SD 53 concurrency |
| Tripp | Jordan Junction | 243.54 | 391.94 | US 183 north / SD 44 west / SD 53 north – Presho | Western end of US 183/SD 44 concurrency; eastern end of SD 53 concurrency |
| Tripp | Winner | 252.70 | 406.68 | SD 44 east – Platte | Eastern end of SD 44 concurrency |
| Tripp | Colome | 263.34 | 423.80 | US 183 south / SD 49 north – Bassett | Eastern end of US 183 concurrency; Southern terminus of SD 49 |
| Gregory | Gregory | 277.92 | 447.27 | SD 47 north / SD 251 south to I-90 | Western end of SD 47 concurrency; Northern terminus of SD 251 |
| Gregory | Burke | 286.03 | 460.32 | SD 47 south – Jamison | Eastern end of SD 47 concurrency |
| Gregory | ​ | 305.22 | 491.20 | SD 1806 north – Whetstone Bay | Southern terminus of SD 1806 |
| Gregory | ​ | 311.99 | 502.10 | SD 43 south – Butte | Northern terminus of SD 43 |
| Gregory | ​ | 320.78 | 516.25 | US 281 south – Spencer, O'Neill | Western end of US 281 concurrency |
| Charles Mix | Pickstown | 332.90 | 535.75 | SD 46 east (297th Street) – Wagner | Western terminus of SD 46 |
| Charles Mix | Lake Andes | 338.98 | 545.54 | SD 50 west – Geddes, Platte | Western end of SD 50 concurrency |
| Charles Mix | ​ | 348.90 | 561.50 | SD 50 east – Wagner | Eastern end of SD 50 concurrency |
| Charles Mix | ​ | 355.87 | 572.72 | US 281 north – Armour | Eastern end of US 281 concurrency |
| Douglas | No major junctions | No major junctions | No major junctions | No major junctions | No major junctions |
| Hutchinson | ​ | 373.94 | 601.80 | SD 37 – Tripp, Parkston | |
| Hutchinson | ​ | 387.70 | 623.94 | SD 25 south – Scotland | |
| Hutchinson | ​ | 402.77 | 648.20 | US 81 – Freeman, Yankton | |
| Turner | ​ | 419.82 | 675.63 | SD 19 south – Viborg | Western end of SD 19 concurrency |
| Turner | ​ | 420.81 | 677.23 | SD 19 north – Hurley | Eastern end of SD 19 concurrency |
| Lincoln | Lincoln–Lynn township line | 435.23 | 700.43 | I-29 south – Beresford | Western end of I-29 concurrency; I-29 exit 62 |
| Lincoln | Lynn Township | 438.25 | 705.30 | I-29 north – Sioux Falls | Eastern end of I-29 concurrency; I-29 exit 59 |
| Lincoln | ​ | 441.72 | 710.88 | SD 115 north / CR 121 south (474th Avenue) – Sioux Falls | Southern terminus of SD 115 |
| Lincoln | ​ | 445.71 | 717.30 | SD 11 north (478th Avenue) – Sioux Falls | Western end of SD 11 concurrency |
| Lincoln | ​ | 446.67 | 718.85 | SD 11 south (479th Avenue) – Alcester | Eastern end of SD 11 concurrency |
| Lincoln | Canton Township | 451.88 | 727.23 | US 18 east – Inwood | Continuation into Iowa |
| 1.000 mi = 1.609 km; 1.000 km = 0.621 mi Concurrency terminus ||||||