The valley of the river has been one of the productive timber regions in Oregon. The lower course of the river passes through the Siuslaw National Forest. Over half of the Siuslaw Watershed is government-managed, primarily Bureau of Land Management (BLM) in checkerboard lands on the eastern side, and Siuslaw National Forest in the mid to western Coast Range.

• The Siuslaw River is about 110 miles long, originating in the mountains of southwestern Lane County, about 10 miles west of Cottage Grove. 
• It flows generally west-northwest through the Central Oregon Coast Range, before entering the Pacific at Florence.
• The watershed basin is approximately 773 square miles.
• The elevation at the source of the river is 636ft. At the mouth, the elevation is 0 feet (sea level).

It is part of the homeland of the Siuslaw People, after whom it is named. Citizens of the Siuslaw Nation lived in villages along the river until 1860, when they were forcibly removed to a reservation in Yachats where their homes, farms, gardens and villages were destroyed and occupied by US settler-colonists.

The river has historically been a spawning ground for Chinook and coho salmon. Over time, due in large part to industrial logging operations and the industry’s careless use of herbicides, salmon numbers have declined. 

The estuary of the river is surrounded by extensive wetlands that are a significant habitat for migratory birds along the coast. It is one of the very few Western Oregon rivers where all major forks are not dammed.