Located in Del Norte and Humboldt counties, the four parks protect the endangered coast redwood (Sequoia sempervirens)—the tallest, among the oldest, and one of the most massive tree species on Earth—which thrives in the humid temperate rainforest.

The parks preserve 37 miles (60 km) of pristine coastline, indigenous flora, fauna, grassland prairie, cultural resources, waterways, as well as threatened animal species, such as the Chinook salmon, northern spotted owl, and Steller's sea lion.

Redwood forest originally covered more than two million acres (8,100 km2) of the California coast, and the region of today's parks largely remained wild until after 1850.

The gold rush and attendant timber business unleashed a torrent of European-American activity, pushing Native Americans aside and supplying lumber to the West Coast.

Modern RNSP management seeks to both protect and restore the coast redwood forests to their condition before 1850, including by controlled burning.

In recognition of the rare ecosystem and cultural history found in the parks, the United Nations designated them a World Heritage Site in 1980.

Local tribes declared an Indigenous Marine Stewardship Area in 2023, protecting the parks region, the coastline, and coastal waters.

Modern-day Native American nations such as the Yurok, Tolowa, Karuk, Chilula, and Wiyot have historical ties to the region,[3] which has had various indigenous occupants for millennia.

[4] Describing "a diversity in an area that size that has probably has never been equaled anywhere else in the world", historian David Stannard accounts for more than thirty native nations that lived in northwestern California.

[25] Jenner says a good team of two men could saw through a redwood tree at about a foot per hour with a crosscut saw, their preferred tool until after World War II.

[c] Organizations formed to preserve the surviving trees:[36] concerned about the sequoia of Yosemite, John Muir cofounded the Sierra Club in 1892.

[38] In 1916, politician William Kent purchased land outright and helped to write the bill founding the National Park Service (NPS).

Historian Susan Schrepfer writes that, in a sixty-year-long marathon, the Save the Redwoods League and the Sierra Club were racing the logging companies for the old trees.

[43] Balancing opponents and supporters, the Save the Redwoods League saw their compromise bill pass in 1923, allowing condemnation for park acquisition with state oversight.

[46] After sustaining a governor's veto in 1925,[45] the league broadened its efforts to include the whole state, mounted a publicity campaign, and gained the support of the Los Angeles Times.

The Save the Redwoods League opposed it, highlighting a division between preservationists who preferred unembellished nature and a segment of the park service who wished to provide recreation and playgrounds for the public.

[62] After intense lobbying of Congress, the bill creating Redwood National Park was signed by President Lyndon B. Johnson in October 1968.

The evaluation committee noted cooperative management and ongoing research in the parks by Cal Poly Humboldt University and other partners.

[86] For many years thought to be the tallest, one specimen named simply "Tall Tree" in Prairie Creek Redwoods State Park was measured at 367.8 feet (112.1 m).

"So many people have stood on the base of the tree that the ground is hard packed", said Professor Stephen C. Sillett of Cal Poly Humboldt university in the 1990s.

[103] About 66 species of land mammals have been documented, including the black bear, coyote, cougar, bobcat, beaver, river otter, and black-tailed deer.

[107][110] The tidewater goby is a federally listed endangered species that lives near the Pacific coastline that were extirpated from the parks in 1968 when shoreline alterations affected the water's salinity.

Frequent minor earthquakes in the park and offshore under the Pacific Ocean have resulted in shifting river channels, landslides, and erosion of seaside cliffs.

[e] They receive abundant rain during most of the year, with a peak in winter, a decrease in June and September, and two dry summer months (July and August).

Increasing average temperatures have led to reduced water quality, affecting the fish and other fauna, and rising sea levels threaten to damage park structures near the coast.

[134] Scientists fear climate change is likely to shift the range in which coast redwoods live to outside protected areas,[135] and many have done research on assisted migration.

[163] Since the 2019 closure of the DeMartin Redwood Youth Hostel, a low-amenities shared lodging facility near Klamath, California,[164] there are no hotels or motels within the parks' boundaries.

[165] NPS itself offers no lodging but for accommodations, links to each town from north to south along US 101: Brookings, Oregon, and in California, Crescent City, Klamath, Orick, Trinidad, McKinleyville, Arcata, Eureka, Ferndale, and the counties of Del Norte and Humboldt.

Proper food storage to minimize encounters with bears is strongly enforced, and hikers and backpackers are required to take out any trash they generate.

[171] Visitors can fish for salmon and trout in the Smith and Klamath rivers, and the beach areas offer opportunities to catch smelt and perch.