MacDonald Pass is on U.S. Highway 12, thirteen miles east of Helena, Montana. It is steep and should be avoided in the winter.
Of course, you could say that RVs should avoid traveling in the winter in the northern Rocky Mountains and I would agree. It goes double for steep roads in the winter.
In the summer, Highway 12 is merely a steep road but I think you should know what you are getting into before you go there. Really the road is very nice, wide and has slow lanes both climbing and descending, and overall the grade alone isn’t a good enough reason to not travel on Highway 12.
Expect large vehicles to be traveling at very slow speeds relative to traffic or speed limits.
Montana interactive map for road conditions. MDT Travel and Weather
Elevation: 6320 feet
Length: 10 miles
Terrain: 8% grades on both the east and west side of the pass. The steepest areas are near the top. The east side of the pass is steeper than the west side. Near the top, eastbound there is a sign recommending low gears and a maximum speed of 25 miles per hour.
Turns: Are mostly gentle with exception of one turn near the top, on the east side, with warning signs for eastbound traffic, to not go fast around the turn. I call this a dump truck turn which is usually preceded by a sign warning truck that roll-over is possible.
Turnouts: One turnout on the west side on at a scenic overlook. Right turn for eastbound uphill traffic.
Turnaround locations: None until at the top
Chain up areas: One on each side serves both east and westbound traffic
Runaway truck ramps: None
MacDonald Pass Our Experience
We drove over MacDonald Pass eastbound on our way to Helena on September 14, 2020. The road was dry and overall, other than slow speeds pertaining to the steepness of the grade we didn’t have any difficulty. Assuming you have enough power to travel the pass and assuming the road is dry, you should not have any problem.
Expect slow climb speeds eastbound in the 35 miles per hour range. Expect slow descent speeds for the first two miles on the east side, eastbound at about 25 miles per hour.
Here is a link to the Montana Department of transportation webcam for MacDonald Pass
Here is our link to our interactive map. Bad Roads for RVs