It was originally 10 miles (16 km) long, with its northern terminus at U.S. Highway 18.

When that route was realigned southward, SD 75 was shortened to 3 miles (4.8 km).

This configuration remained in place until 1976, when it was redesignated as South Dakota Highway 391.

It was located in northeast Harding County, beginning at South Dakota Highway 8 (current SD 20) and extending northward to the North Dakota border.

In 1976, the SD 75 designation was moved approximately 18 miles (29 km) east onto its current alignment, where it remains today; the old segment became part of South Dakota Highway 79.