There are 18 National Natural Landmarks in the U.S. state of Washington, out of nearly 600 National Natural Landmarks in the United States.

Boulder Park

Drumheller Channels

Ginkgo Petrified Forest

Grand Coulee

Mima Mounds

Moses Coulee

Nisqually Delta

Sims Corner Eskers and Kames

Steptoe and Kamiak Buttes

Umtanum Ridge Water Gap

Wallula Gap

Withrow Moraine and Jameson Lake Drumlin Field

Davis Canyon

Washington National Natural Landmarks (clickable map)

Name	Image	Date	Location	County	Ownership	Description
Boulder Park and McNeil Canyon Haystack Rocks		1986	47°52′43″N 119°48′06″W / 47.878611°N 119.801667°W / 47.878611; -119.801667	Douglas	Federal, state	The most illustrative examples of glacial erratics in the United States.
Davis Canyon		1986	48°14′38″N 119°45′06″W / 48.243775°N 119.751774°W / 48.243775; -119.751774	Okanogan	State, private	One of the largest and least disturbed examples of antelope bitterbrush-Idaho fescue shrub steppe remaining in the Columbia Plateau.
Drumheller Channels		1986	46°58′30″N 119°11′47″W / 46.975°N 119.196389°W / 46.975; -119.196389	Adams, Grant	Federal, state, private	Illustrates the dramatic modification of the Columbia Plateau volcanic terrain by late Pleistocene catastrophic glacial outburst floods. Includes Columbia National Wildlife Refuge.
Ginkgo Petrified Forest		1965	46°56′56″N 120°00′10″W / 46.948889°N 120.002778°W / 46.948889; -120.002778	Kittitas	State	Thousands of logs petrified in lava flows. Part of Ginkgo/Wanapum State Park.
Grand Coulee		1965	47°46′00″N 119°13′00″W / 47.766667°N 119.216667°W / 47.766667; -119.216667	Grant	Federal, state, private	An illustration of a series of geological events.
Grande Ronde Feeder Dikes		1980		Asotin	Private	The best example of basalt dikes, the congealed feeder sources of the Columbia River basalt plateau.
Grande Ronde Goosenecks		1980		Asotin	Federal	A 1,500-foot (460 m) deep canyon that follows a tortuous path along meanders.
The Great Gravel Bar of Moses Coulee		1986	47°27′30″N 119°48′00″W / 47.458333°N 119.8°W / 47.458333; -119.8 (Moses Coulee)	Douglas	State, private	Largest and best example of a pendent river bar formed by catastrophic glacial outburst floods that swept across the Columbia Plateau.
Kahlotus Ridgetop		2011		Franklin	State	The best remaining example of the Central Palouse Prairie grassland subtheme.
Mima Mounds		1966	46°53′N 123°03′W / 46.89°N 123.05°W / 46.89; -123.05 (Mima Mounds)	Thurston	State	A prairie containing unusual soil pimples of black silt-gravel.
Nisqually Delta		1971	47°06′31″N 122°42′11″W / 47.108611°N 122.703056°W / 47.108611; -122.703056 (Nisqually Delta)	Pierce, Thurston	Federal, state, tribal, private	An unusually fine example of an estuarine ecosystem. Includes Nisqually National Wildlife Refuge.
Point of Arches		1980	48°14′47″N 124°42′01″W / 48.2464503°N 124.7002419°W / 48.2464503; -124.7002419 (Point of Arches)	Clallam	Federal	An outstanding exhibit of sea action in sculpturing a rocky shoreline. A unit of Olympic National Park.
Rose Creek Preserve		1984		Whitman	Private	The best remaining example of the aspen phase of the hawthorne-cow parsnip habitat type in the Columbia Plateau. Managed by The Nature Conservancy.
Sims Corner Eskers and Kames		1986	47°49′30″N 119°22′00″W / 47.825°N 119.366667°W / 47.825; -119.366667	Douglas	Federal, state, private	The best examples in the Columbia Plateau of landforms resulting from stagnation and rapid retreat of the ice sheet during the last glaciation.
Steptoe and Kamiak Buttes		1965	47°01′57″N 117°17′55″W / 47.0325°N 117.298611°W / 47.0325; -117.298611	Whitman	State, county, private	Isolated mountain peaks of older rock surrounded by basalt, rising above the surrounding lava plateau.
Umtanum Ridge Water Gap		1980	46°51′00″N 120°32′40″W / 46.85°N 120.544444°W / 46.85; -120.544444	Kittitas	Federal, state, private	Geologic formation that illustrates the processes of tectonic folding and antecedent stream cutting.[1]
Wallula Gap		1980	46°02′40″N 118°56′48″W / 46.044444°N 118.946667°W / 46.044444; -118.946667	Benton, Walla Walla	Federal, state, county, municipal	The largest and most spectacular of several large water gaps through basalt anticlines in the Columbia River basin.
Withrow Moraine and Jameson Lake Drumlin Field		1980	47°41′15″N 119°37′29″W / 47.6875°N 119.624722°W / 47.6875; -119.624722	Douglas	Federal, private	The best examples of drumlins and the most illustrative segment of the only Pleistocene terminal moraine in the Columbia Plateau