[freebeard]

I once coasted for the top of Siskyou Pass to the first Ashland exit. I don't know the distance but using a caliper on screen with Apple Maps it looks to be maybe 12.5 miles.

Is Siskiyou Summit challenging?
The road includes some steep sections. Depending on which way you're headed (north or south), the summit gains or loses 2,300 feet in altitude in just six miles on its 6 percent grades. The pass contains a hazardous stretch of the road starting from Milepost 18 of northbound I-5, which has a steep slope of 6%, negotiating a height of 2,000 feet (610 m) in a short road length of 6 miles (9.7 km). The descent along this highway is considered the most dangerous, particularly on foggy nights when visibility is almost next to nothing. In spite of the hazards involved, 13,000 trucks ply this route every day.

www.dangerousroads.org/north-america/usa/3775-siskiyou-summit.html

Six miles at 6%.