Olympic National Park is isolated from other mountain ranges and surrounded by the waters of the Pacific Ocean and Puget Sound; this isolation has allowed the development of endemic species, including Olympic marmot, 4 subspecies of other mammals, 2 subspecies of trout, and 12 species or varieties of plant. 11 major river systems drain the Olympic mountains, offering some of the best habitat for anadromous fish species (such as salmon that live their lives in the sea and migrate to a freshwater river to spawn) in the country.
Reflecting the varied topography (from seashore to glacier) and the varied rainfall, the vegetation zones in the site are complex and varied. The park is divided into two segments: a mountainous core and a separate coastal strip. The rugged features of Olympic National Park are the result of the collision of drifting continental plates.
The area contains a great wealth of geological formations, affected by high rainfall on the west and low rainfall on the east. The lighter shales, sandstones and basalts, which had been violently sheared and squeezed during this tectonic movement, bobbed up like a cork, forming a dome some 95 km in diameter. Deep valleys and canyons were eroded out of this dome and glaciers sculpted the craggy peaks and beautiful cirques to form the spectacular landscape which characterizes the modern Olympics.
The mountains contain about 60 active glaciers; the area is unique in because it is the lowest latitude in the world in which glaciers begin at an elevation lower than 2,000 m and exist below 1,000 m. Glacier-clad peaks interspersed with extensive alpine meadows are surrounded by an extensive old growth forest, among which is the best example of intact and protected temperate rainforest in the Pacific Northwest.
The coastal strip of the site stretches along 80 km of wilderness beach, characterized by rocky headlands, log-strewn beaches, and a wealth of intertidal life; rocky islets along the coast are remnants of a continuously receding, changing coastline, and the arches, caves and buttresses are evidence of the continuous battering of the waves. Tide pools are filled with hundreds of species of invertebrate life, and seals, sea lions, sea otters and several species of whale are often seen in the waves and around the offshore islands.
The main danger to the integrity of the site is, oddly, one of its attractions: the mountain goat. Due to the isolation of the site, mountain goats never dispersed naturally to the Olympics, so their introduction in 1925-29 may be causing significant changes in the natural ecosystem. The mountain goats have reduced plant cover, increased erosion, and shifted plant-community dominants towards more resistant or less palatable species; they have been recorded feeding on at least three of the endemic plants, and some concern has been expressed that these species may be endangered by the mountain goat.
The coniferous forest of Olympic is of prime commercial interest and practically all the original forest outside the park has been harvested.
29 June 1938 as a national park; the Pacific Coastal Area and Queets River corridor were added on 6 January 1953. Accepted as a biosphere reserve in June 1976, and as a World Heritage site in 1981.