US-16A - Iron Mountain Road

US-16A - Iron Mountain Road in Custer, South Dakota is graded at 357 corners, about 10.2 for every mile you drive. 72 of them are genuinely tight (20% of the road), and the sharpest turns in at an 11 m radius.

Graded corners

357

Tight (1–2)

72

Tightest radius

11 m

Corners per mile

10.2

Corners are graded from the route’s own geometry on the rally 1–6 scale, where 1 is a hairpin. Road & Rally calls them out as you drive.