I’d also recommend starting at the upper falls, since the upper falls lot is free. I’d highly recommend walking the trail when you visit, so you can see both viewpoints and appreciate the peaceful forest walk in between. It’s 0.7 miles each way, for a roundtrip of just under 1 ½ miles. The Snoqualmie Falls hike is a short out-and-back route that connects the viewpoint at the top of the falls with the viewpoint at the base of the falls. Another reason for Snoqualmie Falls’ popularity: A TV series called Twin Peaks was filmed here, first in the 90s and then more recently in 2017.
