And I tried soloing Mt. Jefferson last month... to the point of doing it safely and alone.
For Mt. Jefferson, I drove to Salem, took Hwy 22 toward Detriot Lake. At the Detroit
ranger station (on the Hwy) I got my free Pamelia Lake permit and continued on. There's
a limit of 20 people PER DAY allowed to go in via this trailhead. So... call in advance or
go during midweek when permits are likely to be available.
From Pamelia Lake trailhead, I hiked to Shale Lake, cooked some dinner, then continued up to 7000 ft where I bivouaced for the night.
Leaving my bivy site, I climbed snow, loose scree, unstable sand and reached the Red Saddle at 11:30 am. I carried crampons and ice axe, but never used them. I wore a helmet just in case. The scree was easier to walk up than the snow, so I bypassed the snow fields.
The last 400 ft was mostly bouldering. Mostly I went around them. A couple of places I went over them. The drop-offs to right and left are definitely steep. Just be sure-footed and don't stumble. The boulders are solid and secure. The snowfields on either side is also quite steep - 50 to 65 degrees.
I made it to the Red Saddle at 10,200 ft - no problem.
The final 200 feet involves the most dangerous part:
The "Terrible traverse" needs to be crossed to get to the far side. Snow slope is 45 to 60 degrees and it's a LONG LONG slide to the bottom.
That's as far as I cared to go alone.
If you want to solo that final part... carry some snow stakes and rope. Belay yourself carefully. There's nobody around to help you if anything happens.
I've heard people have climbed the final 200 feet, without ropes - when there was no snow on the slope. It's late August now, the snow will likely be gone from the monolith, but I assume there will still be snow on the Terrible traverse.
Pictures were generated by Google Earth. Red line is my GPS-generated path. My pictures were all taken July 28, 2010. Expect less snow.
Two other routes, from Jefferson Park on the north side, Jefferson Glacier and Whitewater Glacier seem less safe. Jefferson glacier is a risky climb with creavasses and steep slopes near top. Whitewater glacier on east side, is a long snow climb and traverse on steep slopes to the Red Saddle. I tried soloing Jefferson glacier, but it didn't seem prudently safe.
I've also tried soloing Three Fingered Jack last year and that too, did not seem safe to summit alone. Until I take some rock climbing classes, I'm happy just getting near the summits.