Continuing with my peakbagging of Sonoma County, Koerber Benchmark caught my eye. I had just hiked the far more noteworthy and lovely Pole Mountain the previous day. In contrast, Koerber Benchmark is more topographically prominent but shorter and far less noteworthy. Hence, this post is probably only relevant to hardcore peakbagger types like me.
Koerber Benchmark Overview
This named summit is a P1K and the fifth most prominent summit of Sonoma County. Curiously, its absent from any peakbagging lists that I typically follow. Thus it flies under the radar for most. A previous complicating factor was access; Monte Rio Redwoods Regional Open Space recently added this section in 2025. Prior to that it was owned and managed by the Mendocino Redwood Company, a logging interest. Additionally, the nearby Upper Willow Creek Unit of Sonoma Coast State Park had opaque permitting issues. Presently (Early 2026) there are no permits or access restrictions to the Upper Willow Creek Unit although maps still indicate so. In any case, Koerber Benchmark is now completely open to the public but remains obscure outside of the peakbagging world.
Its altitude is 1,487' and its prominence is 1,318'. The summit itself is heavily wooded and there's no evidence of an actual benchmark or summit register. Here's the route as I did it, using a loop of Sonoma Coast State Park Trails and Monte Rio Redwoods Regional Open Space. My hike was 9 miles with 1,750' of gain. It was arduous and with challenging routefinding.
I recommend using this map from Sonoma County Parks for guidance. Its detailed and highlights the complete smorgasbord of trails within the two parks. The state park map is still dated.
Trip Report
Trailhead to Sonoma Coast/Monte Rio Redwoods Boundary
I parked here right off Freezeout Road. The road is narrow and it almost looks like a place you shouldn't be. However there were many other cars parked there and I felt relief. I didn't park in the small lot within the gate - just didn't seem right.
I walked the road from Islands in the Sky Trailhead/Gate about 1/4th of a mile to the Islands in the Sky Trail on the right. This trail steeply ascends the highlands of Sonoma Coast State Park. I stayed on this trail for 1.3 miles as it passed many junctions. Eventually the trail enters a high meadow and flattens before linking with the Fern Tree and Badger Hill Vista Trail.
The trail undulates through the high country for about 1.2 miles before reaching the boundary with Monte Rio Redwoods Regional Park. Tagging the "Big Island" Peak along the way brings you to the high point of Sonoma Coast State Park
Monte Rio Boundary to Koerber Benchmark
The trails in Monte Rio Redwoods are well established though not really intuitive. Many of them are single-track and mountain bike oriented. Others are evidently old logging roads. Paths go in every direction with multiple parallel trails and converging trails. Without a map or GPS, its easy to get lost.
The more direct route involves taking Fern Springs Trail from the boundary with Sonoma Coast State Park. Follow this old logging road for about 1 mile as it passes numerous junctions. Look for a junction with "Badfinger" Trail (a mountain biking route). Take this trail for a few hundred yards, then begin a short but nasty bushwhack to the highest point on a relatively flat peak.
The more scenic route is the Sound of Music Trail that basically parallels Fern Springs Trail. From the boundary with Sonoma Coast State Park, take Fern Spring Trail for about 0.4 miles. On the right is the marked junction with Sound of Music West Trail. Walk this through open country with wide ranging views for 0.5 miles. On the left will be a junction for the Koerber Trail - take this for about 0.2 miles until it rejoins with Fern Springs Trail. Go right and look for the Badfinger Trail on the right that gets close to the summit. Again - its a bushwhack to get to the proper high point.
Descent back to the Trailhead
Like getting to the summit of Koerber Benchmark, the descent is not straightforward. From the brushy summit, descend through the brush to get back to the Monte Rio Trail and take it in a north-northwesterly direction. Take this logging road about 1 mile until the junction with Box Springs Trail.
Descend the steep Box Springs Trail about 1.7 miles until it crosses Freezeout Creek and almost immediately junctions with Islands in the Sky Loop. From there, its a 1.0 mile easy return down the road to the trailhead on Freezeout Road.
I look forward to further development of Monte Rio Redwoods Regional Park - hopefully the trails get improved marking!
No Comments