The Snoqualmie Valley Trail (wikipedia) follows an old railroad route from the John Wayne Trail at Rattlesnake Lake to the town of Duvall, WA. The 31-mile trail is mostly packed gravel, with a small on-road portion and largely flat, the only climbing is between I-90 and Rattlesnake Lake.
The gps track available as a gpx or kml if you want to see the route in more detail. Or click here for directions in Google Maps.
The City of Duvall has a nice pdf map of the entire route that shows, mileages, local farms, salmon viewing opportunities, and other trail highlights.
Mileage markers are available along the entire route:
References and Links:
The trail starts at the Cedar Falls Trailhead and descends roughly 4.5 miles to a crossing under I-90.
Once under the freeway, you'll pass through North Bend and the Mt Si Golf Course.
When you cross the bridge over the Snoqualmie River, you'll need to carry your bike down the stairs and begin the on-road detour for a mile or two before picking up the trail again off Tokul Rd. The route is well-signed.
Approaching the bridge:
A rather steep set of stairs to carry your bike down:
Looking back south at the bridge over the Snoqualmie:
The first turn-off onto SE Mill Pond Rd, very lightly travelled and easy to ride.
The connection to Tokul Rd is also well-marked:
You can't actually see the trail when you approach, but there's a path down from the road:
Looking back from the other direction:
Within a mile you'll cross the Tokul Creek Trestle:
From here you pass through the towns of Fall City and Carnation (there are restaurant and gas stations a couple blocks over from the trail, head west from the trail when you reach Nick Loutsis Park) before ending in Duvall for a total of roughly 31 miles.