Big Bear Mountain is a 5,641-foot summit on the western edge of Washington’s North Cascades in the Boulder River Wilderness of Mount Baker-Snoqualmie National Forest, roughly between Three Fingers and Liberty Mountain. Its slopes drain into tributaries of the Sauk and Stillaguamish rivers. The mountain lies in a marine west coast climate shaped by Pacific weather systems forced upward by the Cascades, bringing heavy rain and snowfall, cloudy winters, clearer summers, and wet, avalanche-prone snow. Its rugged landscape reflects a long geologic history: volcanic activity and terrane accretion helped form the range around 50 million years ago, and later glaciation, uplift, and faulting carved the steep terrain and nearby U-shaped valleys.