“A mild, mixed-surface road from Nathrop to St Elmo.
— Matt Giaraffa
This road is paved and a mild grade at the bottom in Nathrop up to Alpine, and railroad grade (3%) for most of it. Around Mt Princeton Hot Springs, there are some steeper sections, but above that, it's back to 3% grade.
The road turns to dirt above Alpine.
The Alpine Tunnel railroad route came up this back in the late 1800's, look for some relics still there, such as the High Lonesome former train depot shorter after the road changes to dirt.