South Dakota Highway 73 (SD 73) is a state route that runs across western South Dakota. It begins at the Nebraska border, north of Merriman, Nebraska, as a continuation of Nebraska Highway 61. It runs to the North Dakota border, where it continues as North Dakota Highway 49. It is just more than 255 miles (410 km) in length.

Quick Facts Highway 73, Route information ...

Highway 73
Route of SD 73 (in red)
Route information
Maintained by SDDOT
Length	255.291 mi[1][2] (410.851 km)
Existed	1926–present
Major junctions
South end	N-61 at the Nebraska border
Major intersections	US 18 in Martin I-90 in Kadoka US 14 in Philip US 212 in Faith US 12 in Lemmon
North end	ND 49 at Thunder Hawk
Location
Country	United States
State	South Dakota
Counties	Bennett, Jackson, Haakon, Ziebach, Meade, Perkins, Corson
Highway system
South Dakota State Trunk Highway System Interstate US State
← SD 71 → SD 75

Close

When designated in the 1920s, South Dakota 73 only consisted of the segment from Faith (U.S. Route 212) to Lemmon (U.S. Route 12). The remainder of the route was unnumbered.

Around 1935, SD 73 was extended south from Faith, absorbing what had been a portion of South Dakota Highway 24 to near Plainview, then southeast via a new route to Philip. From there, it was concurrent with U.S. Highway 16 to Kadoka then southward along what had been South Dakota Highway 63. It continued south to the Nebraska border south of Martin, after sharing an alignment with U.S. Highway 18. Except for minor route straightening and a new concurrency with Interstate 90, this route has not changed since.

Around 1979, the northern terminus was extended east along U.S. 12 to Thunder Hawk, where it met up with a new road to link with ND 49.