Most of the Cedar River Trail follows an old RR right-of-way, but the way we like to do it, we start at the mouth of the Cedar River where it empties into Lake Washington, and follow it all the way to the boundary of the City of Seattle watershed at Landsburg. Depending on the time of the year, there are many places along this trail where you can observe hundreds of sockeye salmon spawn in the fall. A truly spectacular sight; although the odor of spawned-out, dead fish decaying along the shore can be very strong. Seagulls and crows are feasting on the dead fish. The trail runs for 4.5 mi. within the Renton City limits and then continues out into King County.
There is ample parking at either end of the trail and many mid-way points in between. Parking along the fence of the Boeing airplane factory in Renton has lots of parking spaces, two toilet facilities, and a nice view of Lake Washington. There are two places along the trail where once in a while one has to stop on the trail for a brand new Boeing jet airplane crossing, so you better give them the right of way or you get blown away! Starting at the mouth of the Cedar River (N47.50101, W122.21414, elev. 20 ft.) also has the advantage that there is a boat rental place (with permanent facilities and a place where they sell refreshments) where you can rent a kayak or Canoe and venture out onto Lake Washington and get some exercise for your upper body muscles after (or before) pedaling the 17 miles to the end of the Cedar River Trail. There are two stretches along the lower Cedar River Trail where pedestrian and bicycle traffic are separated: from Lake Washington to N. 6th St. and again from the Logan Ave. bridge (0.96 mi., N47.48616, W122.20930) (and Senior Center) to the Renton Library (1.6 mi., N47.48176, W122.20137). Bicycles share the road with automobile traffic in those locations, but that is not a problem. Before getting to the library, it is difficult to cross Bronson Way (a major thoroughfare) above, so it is much safer to dismount and walk the bike for the short stretch through the underpass. Next to the library is a skate park (a former swimming pool) that is quite an attraction for the young folks. The park has facilities and a drinking fountain.
The next road crossing at a busy street has a button-activated crossing signal (1.7 mi., N47.48138, W122.19985). The trail then goes under a semi-active RR track, under the I-405 freeway and arrives at the City of Renton Cedar River Park, which includes the Carco Theater and Community Center, and is adjacent to a swimming pool and water slide fun park. The trail goes over the river and under the freeway at the same time, to the actual starting point of the RR conversion Cedar River Trail. At 2.9 mi. (N47.47663, W122.17998) is Riverview park with facilities (or a portapottie, depending on the time of the year). A pedestrian bridge offers a good view of the river, with interpretive signs about life forms in the river. Shortly beyond the park is an RR bridge over the river, the first of five of this kind along this trail. East of the bridge is a parking area and a trail access point.
The trail and the river are sharing an underpass under Highway 169, sometimes problematic if the river is at flood stage. On the other side one may have to duck for low-flying golf balls, a little bit further at Ron Regis Park (lots of parking) one has to duck for low-flying base balls. At this park are the last facilities for the next 10 miles.
A nice underpass was constructed recently to allow the trail to go under 154th Pl. S.E. (5.2 mi., N47.46618, W122.13753, elev. 160 ft.). From here on the trail parallels Hwy. 169, actually too close for comfort. This mid-section of the trail is the least enjoyable and no person in their right mind would want to walk here. It is OK as a bicycle trail, at least you get through the unpleasant part a lot faster than walking. There are several places where one has a good view of the river, and one place where the river has nibbled on the trail and taken a bite out of it. At one place one can walk on a dike along the river for a short stretch.
At 8.2 mi. (N47.45701, W122.07861, elev. 270 ft.) the trail goes under two overpasses, and next to the second overpass is a small, unpaved parking area, an access to the Cedar River Park Natural Area, but only a wet, trampled path leads from the trail to it. At 11.3 mi. (N47.41854, W122.04606, elev. 360 ft.) is the second RR bridge over the river. At 12.1 mi. in the town of Maple Valley is a large parking area (holding ~50 vehicles) and official trail access point. The trail goes under Hwy. 18 (12.1 mi., N47.40962, W122.03842) and another road and then comes to the third RR bridge over the river at 12.37 mi. (N47.40588, W122.03803, 390 ft. elev.). On the other (east) side of the RR bridge is another trail access point (also called Fred V. Habenicht Rotary Park) with parking for ~20 vehicles, adjacent to Whitte Road, but the parking area is down below and there is no easy way to get from the parking area up on the trail without scrambling up the steep bank next to Bridge No. 3.
The trail then goes over Whitte Road and soon the pavement ends at the junction with the Green Trail (12.9 mi., N47.39845, W122.04321) leading to Wilderness Lake and Four Corners (a very scenic side spur waiting to be connected to Black Diamond). From here on to Landsburg the trail surface is packed gravel and easy to ride on even with a street bike. At 13.7 mi. is RR bridge No. 4 over the river, and at 14.5 is the next bridge (No. 5, N47.38882, W122.01815) with a nice rock at the west end to sit on and eat a snack. At 15.1 mi. (N47.37987, W122.01720) is a crossing of Rock Creek, where salmon cutouts are decorating the bridge fence. At 15.3 mi., just east of the 15-mi. marker, a trail branches off to the south, connecting to the water pipeline trail and a vast network of about 20 miles of nice trails in the Danville-Georgetown area (http://www.frcv.org/) where you could spend an entire day with a map and might still get lost. At 15.6 mi. the trail crosses a road and there are a few parking spaces here. At 16.2 mi. is a nice picnic table with a view of the river. At 16.5 mi. (N47.38422, W121.99163, elev. 530 ft.) is the last of the six RR bridges (No. 6) over the river, with a nice view of the river upstream and downstream in its natural environment with no houses or farms cluttering its banks. At 16.9 mi. (N47.38183, W121.98487) is a gauging station. Between the gauging station and Bridge No. 6 a hiking trail skirts the river and leads to some of the wildest areas of the entire trail system, opposite an alluvial deposit wall where the river erodes the base of the wall and rocks can come tumbling down any moment. At 17.8 mi. (N47.37536, W121.97146, elev. 580 ft.) is the Landsburg parking area and end of the trail at Issaquah-Hobart-Landsburg road. On the other side of Landsburg Rd. S. E. is Landsburg Park with a salmon viewing platform at the rapids that were restored after a weir that impeded progress of the salmon was removed. This upper part of the Cedar River Trail from Maple Valley to Landsburg is the most scenic stretch of any RR conversion trails in the Seattle area anywhere within a 50-mile radius. This is a tru gem.

The Cedar River Trail is now paved (wide, like all rail trails should be) from where it crosses under I 405 to the intersection with the 'Green To Cedar River Trail'. Both trails are bikable, but on ballast from that point on and are very wooded. It is a slight climb most of the way up river, so I would recommend starting down river and working up, so you will have an easier ride back. The trail has some very scenic sections and some other sections along the highway. Part of the trail between I 405 and Lake Washington goes thru downtown and is hard to find/follow and may be closed when the water is high. The section near the Boeing property at Lake Wahington is marked for pedestrians only, but the adjacent road is an acceptable alternative. With only a few road crossings, I had a great time riding this trail.