Benchmark Rock is an informal spot about 3/4 mile up the Elwha River Trail from its beginning at the Whiskey Bend Trailhead. The author Robert L. Wood, in his book Olympic Mountains Trail Guide, refers to the location as Benchmark Rock, in his Elwha Trail section (pg 40). (Note that historically & culturally, the name of this trail is sometimes seen as Elwha Trail, and other times as Elwha River Trail. The Park uses the later name today.)
It’s a small open setting on the forested low SW slope of Hurricane Hill, where the trail passes over a rock shoulder on the slope, with cliffs downslope. A nice Madrona is growing out of the trailside bedrock, there are places to sit, hang-out, and take pictures.
The views from Benchmark Rock include decent peeks down into Anderson Ranch, the eastern flank of Mount Fitzhenry, the lower canyon of Long Creek, and the northern part of Long Ridge.