Pine Hill Ecological Reserve is a 403-acre protected area in the Sierra Nevada foothills of El Dorado County, established in 1979 as the central state-owned unit of the larger Pine Hill Preserve. It was created to protect rare plants and the unusual gabbro soils that sustain them, part of a broader belt formed about 175 million years ago. The reserve grew from a late-1970s conservation campaign after rare summit plants were damaged by bulldozing. Nationally significant for plant diversity, the preserve protects eight rare plant species, four found only in the Pine Hill area. Access is limited to guided tours because of the plants’ rarity, vulnerability, and surrounding private property.