Access and other info in my post on Quartz Creek Ridge
Continuing our hike from Quartz Creek Ridge, at the access trail junction Bill K7WXW and I retrieved my stashed water, had a small break from the aggressive climb up from the ridge saddle, and then continued north on the Summit Prairie Trail.
Activated Quartz Creek Ridge with Bill (K7WXW) this last weekend. This summit is easily doable with North Quartz Creek Ridge in the same day. Access for both summits is in the middle on a sometimes-not-mapped trail, TH at 46.24186, -121.72969 . This trail system is mixed-use. We saw ultramarathon runners (Dark Divide Ultra), mountain bikers, and dirtbikes. Prepare your ankles accordingly, the trail is often a narrow rut through the dirt because of the motorcycle traffic.
Located just SSE of Mt. St. Helens, Mt. Digital is an easily handled 4-pointer that could be added to multi-summit day along with Marble Mtn, Coaxial Mtn, Break-In Peak (I did this the same day as a drive-up), or Aurora Mtn. All accessible from NF83 and it's branches.
After my success over at Break In Pk., I continued on to Lone Butte to give it another go, after my previously failed attempt. Access remains the same, only take the road in if PNW pinstriping is something you like to adorn your paint.
In a normal year, this would be an easy 4-point drive-up. Driving access is via Forest Road 8303 (Ape Cave Rd.), 8303340, and 8303341. From the end of 8303341 the summit is ~500' to the NW, where the trail ducks off the ridgeline you would just continue straight to the summit.
A storm in recent years has washed out a section of FR 8312 just beyond the Marble Mountain Snowpark. At the edge of the parking lot, where the road begins, the Forest Service has placed several jersey barriers and a locked gate. It appears that there are no plans to repair this section of the road. The only other access to Marble Mountain is from the south, via timber lands owned by Pope Resources / Rayonier. All of the access roads from the south are gated and open only for logging activity, or the few residents that live in the middle of the timber land.
Spencer Butte is the site of a former fire lookout in the Gifford Pinchot National Forest, just north of the town of Northwoods. At the time of my attempt, the simplest access is to go north on FR 25, turn onto FR93 (if you go through the winter gates on 25, you just missed it), and follow 93 to the trailhead. This route is mostly paved, just a short section of gravel from the Muddy River up to the junction with road 9039.
Lone Butte is a "small" hill in the Gifford Pinchot National Forest. It is easily accessible from the Columbia River Gorge via Wind River and NF30, or from I-5 up the Lewis River Hwy to Northwoods and then NF90/Curly Creek Rd. (which connectes to NF30). There is a large area for parking where road 401 cuts to the West. If you aren't particular about your vehicles paint, the road is driveable to an old rock quarry at the west end of Lone Butte, there are some ruts a short way into the road, but they are easy to straddle and most any vehicle could make it past.