Sourdough Mountain, Mountain summit in North Cascades National Park, Washington, United States.

Sourdough Mountain is a 6,111-foot (1,863 m) summit in North Cascades National Park, Washington. Its slopes rise through the marine west coast climate zone of the western Cascades, where Pacific fronts drop heavy, wet snow and raise avalanche danger in winter. Near the top stands the Sourdough Mountain Lookout, a 4.33 m × 4.33 m wooden cabin built in 1933 on a rock, with a shingled roof and diagonally braced shutters that open for observation in all directions.

A smaller shelter stood near the summit from 1917 until it was torn down to make way for the present lookout, built in 1933 by the Civilian Conservation Corps to spot forest fires early. The 4.33 m by 4.33 m cabin sits on a rock, has a wooden shingle roof and diagonally braced shutters that open for observation in every direction. It was listed on the National Register of Historic Places in 1989 and is no longer used for fire detection.

The 1933 lookout near the summit is a small 4.33 m × 4.33 m cabin on a rock, with a wood-shingle roof and diagonally braced shutters that open for observation in all directions. It no longer serves fire detection but is often visited by hikers on the 8.0 km trail. It was listed on the National Register of Historic Places in 1989.

The lookout is reached by an 8.0 km (5 mi) trail, so plan a full day for the climb and return. Snow tends to be wet and heavy on this side of the Cascades, raising avalanche danger in winter and spring. Summer often brings little or no cloud cover, while winter is usually cloudy.

The 1933 lookout replaced an earlier shelter that had stood since 1917 and was torn down to build the present cabin. The cabin sits on a rock, measures 4.33 by 4.33 metres, has a wooden shingle roof and diagonally braced shutters that open for observation in every direction.