Starts in Packwood, Washington, just south of Mt. Rainier National Park. Climbs up lightly traveled roads to a place called Windy Ridge, overlooking Mt. St. Helens. The portion near Windy Ridge is in the "blast zone" from the eruption of Mt. St. Helens - lots of downed trees.

I did this ride last year - it's a great ride, though it's a chore to get to Packwood.

Packwood isn't really close to anything (2.5 to 3 hours from either Portland or Seattle).

http://www.cascade.org/EandR/hpc/Details.cfm

If someone had time to do a weekend of it, you could do a ride in Mt. Rainier National Park on Saturday and then do the High Pass Challenge on Sunday.