The South Fork joins the main Snowqualmie River just north of North Bend.
The Snoqualmie River is 45 miles long and runs roughly southeast to northwest in western Washington State and passes not from North Bend and Interstate 90.
The “Welcome to Twin Peaks” sign from the TV show was on the north side of the main river by the Three Forks Natural Area a mile or two north of North Bend and right across from where the South Fork flows into the Snoqualmie.
