Iron Mountain Road (US 16A): open or closed?
Scenic road · Custer State Park to Mount Rushmore · Black Hills
Current status: Partly open
SD511 reports a closure on part of Iron Mountain Road (US 16A): US-16A at Junction South Dakota 40-Keystone (mile 33.83). The other mapped segments report Dry/Normal.
SD511 map: segment 113130 (Dry/Normal) · segment 113136 (Dry/Normal) · segment 113133 (Dry/Normal)
Official wording or data we matched:
SD511 closure (flagged as a closure on the SD511 map): US-16A at Junction South Dakota 40-Keystone. Restrictions: bridge construction. Restrictions include: width limit 12 ft and length limit 50 ft until further notice. Road work will begin on September 8th 2026. Beginning October 5th the road will be closed to remove the structure. A detour route will be available.
SD511 road condition, segment 113130 "US16A: Jct SD36 to Jct US16" (miles 16.21–29.12): Dry/Normal (code normal_seasonal)
SD511 road condition, segment 113133 "US16A: Jct SD36 to Jct US16" (miles 29.12–29.85): Dry/Normal (code normal_seasonal)
Checked Oct 31, 2026, 12:21 PM CDT (Central time). Sources: Custer State Park scenic drives (SD Game, Fish & Parks) · SD511 road conditions by segment (SDDOT) · SD511 road-condition segment list (SDDOT) · SD511 event lines with closure flags (SDDOT) · SD511 road closures and obstructions (SDDOT) · SD511 road disturbances (SDDOT) · SD511 road restrictions (SDDOT) · SDDOT press releases (latest page)
Current official notices
- SD511 US-16A: Restrictions: bridge construction — US-16A at Junction South Dakota 40-Keystone. Restrictions: bridge construction. Restrictions include: width limit 12 ft and length limit 50 ft until further notice. Road work will begin on September 8th 2026. Beginning October 5th the road will be closed to remove the structure. A detour route will be available. source
About this place
A 17-mile stretch of US 16A linking Custer State Park and Mount Rushmore, known for its "pigtail bridges" and three tunnels that frame Mount Rushmore. SD GFP lists 60+ minutes of travel time.
Tunnels (SD GFP): Doane Robinson (12 ft 0 in wide, 11 ft 4 in high), C.C. Gideon (11 ft 6 in wide, 10 ft 9 in high) and Scovel Johnson (10 ft 9 in wide, 11 ft 0 in high).
Official links: Custer State Park scenic drives (SD GFP) · SD511 road conditions · SDDOT US 16A Keystone project · Road conditions: dial 511 or see SD511
Winter notes
- Game, Fish & Parks says Iron Mountain Road closes periodically in winter, depending on conditions and how quickly it can be cleared safely.
- In Keystone, US 16A is closed at the SD 40 intersection for a bridge replacement (SDDOT says until about April 2027), with a detour and a 12-foot width limit, so plan your route into Keystone.
Opening and closing history
| Date | What happened | Official source |
|---|---|---|
| Oct 5, 2026 | Iron Mountain Road closed for most of the day for SDDOT tunnel inspections (Doane Robinson, C.C. Gideon and Scovel Johnson tunnels). | SDDOT press release, Sept 24, 2026 (read Oct 31, 2026) |
| Oct 5, 2026 | US 16A in Keystone closed at the SD 40 intersection for a bridge replacement, with a detour; SDDOT says it is scheduled to reopen by April 2027. This is in Keystone, at the north end of US 16A, not on the Iron Mountain Road section itself. | SDDOT press release, Sept 28, 2026 (read Oct 31, 2026) |
| Apr 3, 2026 | A two-mile construction closure on US 16A inside Custer State Park (about 14 miles east of Custer) reopened to traffic. This is the park section of US 16A, not the Iron Mountain Road section. | SDDOT press release, March 31, 2026 (read Oct 31, 2026) |
These are the dated official notices we have found so far. Winter weather closures are not announced on a fixed schedule. Only dates read on official pages are listed; we do not fill gaps with guesses.
When to go, month by month
General estimate, not measured data. Crowd and season notes are general estimates from typical patterns and official descriptions, not counts or forecasts.
| Month | Notes (general estimate) |
|---|---|
| January | Can close at times after snow; check SD511. |
| February | Can close at times after snow; check SD511. |
| March | Mixed; snow is still possible. |
| April | Usually drivable; snow still possible. |
| May | Getting busier toward Memorial Day. |
| June | Busy, slow traffic through tunnels. |
| July | Peak season; go early or late. |
| August | Very busy, especially early August. |
| September | Busy weekends, calmer weekdays. |
| October | Fall color, fewer crowds. |
| November | Quiet; first snows can close it briefly. |
| December | Quiet; can close at times after snow. |
How we check
Open when every SD511 road-condition segment for US 16A from Jct SD 36 toward Keystone through Keystone (miles 16.2–35.5, which covers the Iron Mountain Road section) reports an explicit passable condition (Dry/Normal or Wet) in a file updated within 6 hours, and no SD511 closure, NPS alert or recent SDDOT release reports a closure there. Closed or Partly open when SD511 marks segments Closed or posts a closure within those mile markers. Unknown with winter conditions (it closes periodically in winter) or when anything is missing or conflicting. We check official sources about once a day; see our method.
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