Washington is the north-westernmost state of the contiguous United States. Its northern border lies mostly along the49th parallel, and then via marine boundaries through the Strait of Georgia, Haro Strait, and Strait of Juan de Fuca, with the Canadian province of British Columbia to the north. Washington is bordered by Oregon to the south, with the Columbia River forming the western part and the 46th parallel forming the eastern part of the southern boundary.

To the east, Washington borders Idaho, bounded mostly by the meridian running north from the confluence of the snake River and Clearwater River (about 116°57′ west), except for the southernmost section where the border follows the Snake River. To the west of Washington lies the Pacific Ocean. Washington was a Union territory during the American Civil War, although it never actually participated in the war.

Forests cover 52% of the state’s land area, mostly west of the North Cascades. Approximately two-thirds of Washington’s forested area is publicly owned, including 64% of federal land. Other common trees and plants in the region are camassias, Douglas fir, hemlock, penstemon, ponderosa pine, western red cedar, and many species of ferns.^[20] The state’s various areas of wilderness offer sanctuary, with substantially large populations of shorebirds and marine mammals. The Pacific shore surrounding the San Juan Islands are heavily inhabited with killer, gray and humpback whales.

Mammals native to the state include the bat, black bear, bobcat, cougar, coyote, deer, elk, gray wolf, moose, mountain beaver, muskrat, opossum, pocket gopher, raccoon, river otter, skunk, and tree squirrel. Because of the wide range of geography, the State of Washington is home to several different ecoregions which allow for a varied range of bird species. This range includes raptors, shorebirds, woodland birds, grassland birds, ducks, and others. There have also been a large number of species introduced to Washington, dating back to the early 1700s, including horses and burros. The channel catfish, lamprey, and sturgeon are among the 400 known freshwater fishes. Along with the Cascades frog, there are several forms of snakes that define the most prominent reptiles and amphibians. Coastal bays and islands are often inhabited by plentiful amounts of shellfish and whales. There are five species of salmon that ascend the Western Washington area, from streams to spawn.

Washington has a variety of National Park Service units. Among these are the Alta Lake State Park, San Juan Islands National Wildlife Refuge, as well as three national parks, the Olympic National Park, North Cascades National Park, and Mount Rainier National Park. The three national parks were established between 1899 and 1968. Almost 95% (876,517 acres, 354,714 hectares, 3,547.14 square kilometers) of Olympic National Park’s area has been designated as wilderness under the National Wilderness Preservation System. Additionally, there are 143 state parks and 9 national forests, run by the Washington State Park System and the United States Forest Service. The Okanogan National Forest is the largest national forest located on the West Coast, encompassing 1,499,023 acres (606,633 ha). It is managed together as the Okanogan–Wenatchee National Forest, encompassing a considerably larger area of around 3,239,404 acres (1,310,940 ha).