Washington occupies the northwestern corner of the contiguous United States and is bordered by British Columbia to the north, Idaho to the east, Oregon to the south, and the Pacific Ocean to the west. It also includes the intricate inland waters of Puget Sound, the Strait of Juan de Fuca, and the San Juan archipelago, giving the state an unusually complex shoreline and maritime geography.
The Cascade Range divides the state into two broad physical regions. Western Washington includes coastal areas, the Olympic Peninsula, Puget Sound lowlands, and dense coniferous forests. This side of the state is generally wetter, greener, and more urbanized. Eastern Washington lies in the rain shadow of the Cascades and includes rolling plateaus, river valleys, shrub-steppe landscapes, and more continental climate patterns.
Major mountain systems include the Cascades and the Olympics. The Cascade volcanic arc includes Mount Rainier, Mount Baker, Mount Adams, Mount St. Helens, and Glacier Peak. These peaks are part of the geologically active Pacific Ring of Fire. The Olympic Mountains rise sharply from the peninsula and contain some of the state’s most dramatic alpine and temperate rainforest landscapes.
The Columbia River is Washington’s dominant river system and forms much of the southern boundary with Oregon. Other important rivers include the Snake, Yakima, Spokane, Skagit, Cowlitz, and Chehalis. Washington’s natural resources have historically included timber, fish, hydropower potential, fertile soils, and minerals, though environmental regulation and ecological conservation have significantly shaped their use.
The state contains several major ecological zones: Pacific coastline, temperate rainforest, lowland urban estuary, alpine and subalpine mountain environments, dry interior basin, and irrigated agricultural valleys. This diversity makes Washington one of the most ecologically varied states in the country.