Washington is the northwestern-most state of the contiguous United States. Its northern border lies mainly along the 49th 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 borders Oregon to the south, with the Columbia River forming most of the boundary 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.[4]

 

Washington is in the region known as the Pacific Northwest, a term which often includes part or all of British Columbia in Canada and part of Alaska. Sometimes it refers only to lands within the Northwestern United States, including Oregon but the term properly includes British Columbia and Southeast Alaska (the Panhandle) and in some reckonings includes Idaho, the western counties of Montana, the northern counties of California, and the Yukon Territory.
Digitally colored elevation map of Washington.

 

The high mountains of the Cascade Range run north-south, bisecting the state. Western Washington, west of the Cascades, has a mostly marine west coast climate with relatively mild temperatures, wet winters, and dry summers. Western Washington also supports dense forests of conifers and areas of temperate rain forest. In contrast, Eastern Washington, east of the Cascades, has a relatively dry climate with large areas of semiarid steppe and a few truly arid deserts lying in the rainshadow of the Cascades; the Hanford reservation receives an average annual precipitation of between six and seven inches (178 mm) . Farther east, the climate becomes less arid. The Palouse region of southeast Washington was grassland that has been mostly converted into farmland. Other parts of eastern Washington are forested and mountainous.

 

The Cascade Range contains several volcanoes, which reach altitudes significantly higher than the rest of the mountains. From the north to the south these volcanoes are Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams. Mount St. Helens is currently the only Washington volcano that is actively erupting; however, all of them are considered active volcanoes. Nestled amongst the hills are the Galena chain lakes.

 

Washington's position on the Pacific Ocean and the harbors of Puget Sound give the state a leading role in maritime trade with Alaska, Canada, and the Pacific Rim. Puget Sound's many islands are served by the largest ferry fleet in the United States.

Washington is a land of contrasts. The deep forests of the Olympic Peninsula, such as the Hoh Rain Forest, are among the only temperate rainforests in the continental United States, but the semi-desert east of the Cascade Range has few trees. Mount Rainier, the highest mountain in the state,[3] is covered with more glacial ice than any other peak in the lower 48 states.