[4] The Sultan River's drainage basin was subjected to intense glaciation during the Pleistocene era.

The upper South Fork Sultan River flows through a classic U-shaped valley cut by a glacier through Quartz diorite.

The Sultan's river main tributaries—the North Fork, South Fork, Elk Creek, and Williamson Creek— flow through narrow valleys to converge in the lower Sultan basin where the valley floor is relatively broad.

[5] Pleistocene glaciers spread down the valleys of the Sultan River and its tributaries, merging in the lower basin.

Spada Lake, held back by the Culmback Dam, is the main source of drinking water for people in Everett.

Gold deposits were recovered from gravels along the lower river with small-scaler placer operations as early as 1869.

A rough 20-mile (32 km) long wagon road was built from the mine to the railroad at Sultan on the Skykomish River.

[10] A diversion dam on the river was constructed in 1929 by the Everett city government to fill Chaplain Reservoir to the west.