Kinda confusing, since Hipcamp lists the lower, first-come first-served part of the campground. Upper sites are reservable, but are rarely full. Some in the upper part are on rather steep ground with small parking pads, and tight corners. Could be a bit of a struggle for some bigger equipment or tents.
You do get freeway noise, unfortunately. But it's still nice, and is one of the cheaper CA state parks for a campsite with shower.
The road up to the viewpoint (and trailhead for some hikes) is also steep and narrow, and it has little room for vehicles going in opposite directions to pass, so be very careful. And don't try it with something huge.
The Castle Crags were formed in much the same manner as nearby Mt. Shasta and the other peaks of the Cascade Range—by volcanic activity some 200 million years ago. For the last million years, the Crags have been subjected to the forces of wind, rain, ice and even some small glaciers, which have shaped the granite into its distinctive shapes. Rising beside the spiky peaks is a round one, Castle Dome, which many mountaineers liken to Yosemite’s Half Dome.
In 1855, the territory below the Crags was the site of a struggle between local native people and settlers. The locals, armed only with bows and arrows, were driven from their land in a one-sided battle that was chronicled by Joaquin Miller, “poet of the High Sierra.”
Mining—ﬁrst gold, later mercury and chromite—and logging, were the chief industries around the Crags for a hundred years. During the 1920s and 1930s, conservationists worked to protect the Castle Crags; they circulated photographs of the scenic spot and promoted the idea of a comprehensive California state park system.
Exploitation of the land by lumber and mining operations encouraged concerned citizens in 1933 to acquire much of the land, which would eventually become Castle Crags State Park. However much of the crags themselves are part of the Castle Crags Wilderness Area within the Shasta-Trinity National Forest, managed by the U.S. Forest Service.