Part of the King County Regional Trail system, the Snoqualmie Valley trail extends from Duvall all the way to Rattlesnake Lake in North Bend along the old Milwaukee Railroad bed. As a former railroad bed, the trail is wide and flat, with no a grade no steeper than 2% -- barely noticeable. It crosses a number of old bridges and trestles, though, which have solid surfaces and railings that the old railway never provided. Much of the trail's length is lined by trees and fields, but as it passes through towns you may encounter road crossings; one section between North Bend and Fall City is missing, and horseback trail users who wish to travel through must take the road (Tokul/Mill Pond/Meadowbrook Rd/Park Street) for a number of miles before rejoining the railroad bed again through the Three Forks Natural Area. (There are stairs to get back to the trail trestle over the Snoqualmie River at Mill Pond/Reinig Road, but they're impassible to horses.)
Currently, there are only two good parking areas for horse trailers in the north section of the trail: the Griffin Creek Natural Area off 11th Street NE, and the Fall City Park north of Fall City (see status note below regarding this one). More good horse trailer parking spots near the north end of the trail would be a good thing. I'm told there's often room at the public fishing parking at the north end of Duvall, the second left after Cherry Valley Road splits off to the right. At the extreme south end of the trail, you can also park at Rattlesnake Lake Recreation area (directions) and ride back northwards along the trail towards North Bend.
The Snoqualmie Valley Trail is mostly open, except some upgrades to the Tokul Creek trestle maintenance at the south end: closed between 356th Dr SE and Tokul Road. Work is expected to be complete in Spring 2016.
Trail access from the Fall City Park through SE 39th Place has been in dispute recently, but is now open once more. Note there are two logs you must step over to get around the gate at the end of SE 39th Place.
Griffin Creek: From Hwy 203 in Carnation, turn west onto 11th Street NE. In just a few dozen yards, the main road veers left; continue straight on the now-dirt 11th (go slow to keep dust down). In less than a 1/4 mile, you will see signs for Griffin Creek Park Natural Area; the parking area is on the left. This parking area is a maze of passages through trees, there is actually more room here than it appears at first.
Fall City Park: From Fall City, go NE over the river to the roundabout and follow the signs to 203 north towards Carnation. About 200 feet from the roundabout, turn left into the entrance to Fall City Park. There is a gravel parking lot immediately on the left, but better horse-trailer parking can be found by following the road as it curves around to the right; across from the horse arena is a circular gravel road where you can pull in and out easily. A trail from this area leads straight back out to 203 and the equestrian crosswalk to get to SE 39th Place.
Length: 31.5 miles
Surface: gravel, with occasional hard surface trestles and road crossings
Share with: walkers, joggers, bicycles
Parking for: 8+ horse trailers
King County Parks:
KC Parks Snoqualmie Valley Trail site
Griffin Creek Natural Area:
http://www.kingcounty.gov/environment/waterandland/natural-lands/ecological/griffin-creek-plan.aspx
Map:
Snoqualmie
Valley Trail Map PDF