The Redwood National and State Parks (RNSP) are a complex of one national park and three California state parks located in the United States along the coast of northern California. The combined RNSP contain 139,000 acres (560 km2), and include Redwood National Park, Del Norte Coast Redwoods State Park, Jedediah Smith Redwoods State Park, and Prairie Creek Redwoods State Park. Located within Del Norte and Humboldt counties, the four parks protect 45 percent of all remaining coast redwood (Sequoia sempervirens) old-growth forests. The species is the tallest, among the oldest, and one of the most massive tree species on Earth. The parks preserve other indigenous flora, fauna, grassland prairie, cultural resources, waterways, and 37 miles (60 km) of pristine coastline. In 1850, old-growth redwood forest covered more than two million acres (8,100 km2) of the California coast. The northern portion of that area was originally inhabited by Native Americans who were forced out of their land by gold seekers and timber harvesters. The enormous redwoods attracted timber harvesters to support the gold rush in more southern regions of California and the increased population from booming development in San Francisco and other places on the West Coast. After many decades of unrestricted clear-cut logging, serious efforts toward conservation began. By 1918, the work of the Save the Redwoods League, founded to preserve remaining old-growth redwoods, resulted in the establishment of Prairie Creek, Del Norte Coast, and Jedediah Smith Redwoods State Parks among others. The federally managed Redwood National Park was created in 1968, by which time nearly 90 percent of the original redwoods had been logged. In 1994, the National Park Service (NPS) and the California Department of Parks and Recreation (CDPR) combined Redwood National Park with the three abutting Redwoods State Parks as a single administrative unit for the purpose of cooperative forest management and stabilization of forests and watersheds. The ecosystems of the RNSP preserve a number of threatened animal species, such as the tidewater goby, Chinook salmon, northern spotted owl, and Steller's sea lion, though the tidewater goby and the candlefish are believed to have been extirpated from the park in 1968. In recognition of the rare ecosystem and cultural history found in the parks, the United Nations designated them a World Heritage Site in 1980.