U.S. Route 81 is a major north-south highway that extends for 1220 miles in the central United States and is one of the earliest United States Numbered Highways established in 1926 by the US Department of Agriculture Bureau of Public Roads.
South Dakota Highway 44 (SD 44) is a state highway in southern South Dakota that runs from U.S. Route 385 (US 385) west of Rapid City to Interstate 29 (I-29) south of Sioux Falls. It is just more than 379 miles (610 km) long.
South Dakota Highway 471 (SD 471) is a 22.085-mile-long (35.542 km) state highway in the southwestern part of the U.S. state of South Dakota. It travels from SD 71 southeast of Rumford to U.S. Route 18 (US 18) in Edgemont.
South Dakota Highway 43 (SD 43) is a 1.131-mile-long (1.820 km) state highway that exists entirely in the southern part of Gregory County in the southern part of the U.S. state of South Dakota. It begins as an extension of Nebraska Highway 11 (N-11) at the Nebraska state line south of Fairfax. It travels northwest to an intersection with U.S. Route 18 (US 18) south-southwest of the town.
South Dakota Highway 45 is a state route that runs north to south across much of central South Dakota. The northern terminus is at the North Dakota border as a continuation of North Dakota Highway 3, and runs south to South Dakota Highway 44 at Platte. It is 198 miles (319 km) in length.
South Dakota Highway 47 is a state route that runs north to south across the central portion of South Dakota. It begins at an unnumbered highway at the North Dakota border north of Eureka, and ends at the Nebraska border, where it becomes Nebraska Highway 137. It is just under 241 miles (388 km) in length.
South Dakota Highway 48 is a short state route in the far southeast corner of the U.S. state of South Dakota. The route, which runs entirely through Union County, begins at Interstate 29 about 2.5 miles (4.0 km) west of Spink, and becomes Big Sioux River Road, formerly Iowa Highway 403, northwest of Akron, Iowa. It is 12 miles (19 km) in length.
South Dakota Highway 53 is a state route that runs north to south across south central South Dakota. It consists of two separate segments:
South Dakota Highway 25 (SD 25) is a 194.524-mile-long (313.056 km) state highway in the eastern part of the U.S. state of South Dakota. It connects Scotland, Howard, De Smet, and Webster.
South Dakota Highway 15 (SD 15) is a 67.562-mile-long (108.730 km) state highway in the northeastern part of the U.S. state of South Dakota. It connects Clear Lake, Milbank, and Wilmot.
South Dakota Highway 50 is a state route serving south central and southeast South Dakota. The current alignment begins at the junction of South Dakota Highway 34 at "Lee's Corner" east of Fort Thompson, and ends at the Iowa border near Richland, where it continues as Iowa Highway 3. It is about 212 miles (341 km) in length.
South Dakota Highway 19 (SD 19) is a 86.974-mile-long (139.971 km) state highway in the southeastern part of the U.S. state of South Dakota. It connects the Nebraska state line, south of Vermillion, with the southeastern part of the Madison area, via Viborg, Hurley, Parker, and Humboldt. SD 19 formerly entered Centerville, but was shifted to the south. Its former path was redesignated as SD 19A. Its former southern terminus was at Vermillion, but was extended when a new bridge from Nebraska opened.
South Dakota Highway 36 is an east–west state route located in southwest South Dakota. It begins at the junction of U.S. Route 16A on the eastern edge of Custer State Park, and ends at South Dakota Highway 79 just south of Hermosa. It is slightly over nine miles (14 km) in length.
South Dakota Highway 42 (SD 42) is a segmented state highway in southeastern South Dakota. The first segment is a six-mile-long (9.7 km) highway in Aurora County. The second and longest is 60 miles (97 km) long and connects Ethan and Sioux Falls. The final segment connects Sioux Falls to Iowa Highway 9 southeast of Rowena.
Interstate 29 (I-29) is a north–south Interstate Highway in the midwestern United States. In the U.S. state of South Dakota, I-29 traverses on the eastern side of the state from the Iowa border near Sioux City to the North Dakota border near New Effington. On its route, I-29 passes through western portions of Sioux Falls, the state's largest city. Interstate 229, the highway's lone auxiliary route in South Dakota, serves as a bypass around southern and eastern Sioux Falls.
South Dakota Highway 40 (SD 40) is a state highway in southwest South Dakota. The highway is just over 37 miles (60 km) long and runs from U.S. Route 16A (US 16A) in Keystone to Bureau of Indian Affairs Highway 41 in Red Shirt. The highway runs near Mount Rushmore National Memorial in Keystone, and its eastern terminus is on the Pine Ridge Indian Reservation near the edge of Badlands National Park. SD 40 was established along its current route in 1976; the SD 40 designation was originally used on a highway that is now part of SD 44.
South Dakota Highway 71 (SD 71) is a 35.59-mile-long (57.28 km) state highway in the southwestern part of the U.S. state of South Dakota. It travels from the Nebraska state line, where it continues as N-2/N-71, through the Black Hills National Forest, to U.S. Route 18 Bypass in Hot Springs. The road was originally a part of SD 87. It became SD 71 in 1962.
