South Dakota Highway 240
|Maintained by SDDOT|
|Length:||40.033 mi (64.427 km)|
|West end:||I-90 at Wall|
|SD 377 at Badlands National Park|
South Dakota Highway 240, (SD 240) the "Badlands Loop", is located in southeast Pennington and northwest Jackson Counties of southwestern South Dakota. It runs through the eastern portion of the Badlands National Park.
Route description 
SD 240 begins in Wall at exit 109 of Interstate 90 (I-90). From this point, it travels south to Badlands National Park, where it turns southeast. At the Badlands Headquarters at Cedar Pass, South Dakota 240 turns northeast, ending at exit 131 of I-90 near Cactus Flat. The total length of South Dakota 240 is 40 miles (64 km). Because South Dakota 240 enters a national park, there is an entrance fee at either side of the park. The fee is $15 per passenger vehicle, good for 7 days.
Eastern portions of the route that are currently SD 240 (generally from the park headquarters to Cactus Flat) were originally part of the original alignment of SD 40. Construction began in the early 1930s. By 1944, a gravel surface was on Badlands Loop alignment, and by the late 1940s, the Badlands Loop was signed as U.S. Highway 16 Alternate (US 16 Alt.), in addition to SD 40 along the eastern portion of the Loop. These two numbers were used until the early 1970s, when the SD 40 number was replaced by an extension of SD 44 (which entered the park from the southeast rather than the northeast).
Around 1980, US 16, which ran concurrently with Interstate 90, was truncated at its eastern end to Rapid City. Since the US 16 Alternate no longer met the parent route, the route number was changed to SD 240.
Major intersections 
||Wall||0.000||0.000||I-90 / US 14|
||Badlands National Park||31.512||50.714||SD 377 south|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|