Complex sentence: Rancho Del Oso Nature and History Center interprets the cultural and natural history of the area of Rancho del Oso--ranch of the bear--which became part of Big Basin Redwoods State Park, California's oldest state park in the 1970s.
Split into simpler sentences: Rancho Del Oso Nature and History Center is a newer section of California's oldest state park Big Basin Redwoods State Park. The area of Rancho del Oso--ranch of the bear--became part of Big Basin in the 1970s.