Castle Crags Wilderness is a federally protected area in northwestern California within Shasta-Trinity National Forest, set aside in 1984 under the California Wilderness Act. Known for its granite spires, glacially shaped terrain, and varied elevations, it spans a striking landscape along the Sacramento River. The crags also hold a long human history, from Wintu tradition and Spanish naming to the 1855 Battle of Castle Crags, early mineral-springs tourism, railroad resorts, logging, and mining. Rich in biodiversity, the wilderness supports hundreds of wildflower species and diverse wildlife, and today it is valued for hiking, climbing, and backcountry travel, including a 19-mile stretch of the Pacific Crest Trail.