This is a long fire road climb up to the top of Mt. Wilson. It just keeps going and going. The grade is pretty consistently around 10%. From the bottom up to Henninger Flats is about 2.5 miles of wide open fire road with no shade. When you reach Henninger Flats, you'll find some large trees, picnic tables, a water fountain, and the Henninger Flats Museum.
As you continue up, you'll find a split in the fire road. Keep right and climb. Near the top, you'll find a bit more shade in spots. The view is fantastic on a clear day as you come around to the south side of the ridge and climb the final section to the top.
At about 7.5 miles, you'll intersect with the Mt. Wilson Trail
. Keep left and rejoin onto the Mt. Wilson Toll Road in about 0.5 mile.
There is a great lookout at the top. Be sure to check out the Mt. Wilson Observatory if you have time.