I-90 Trail (John Wayne/Iron Horse Trail) - Section 5

This picture shows the general route from Iron Horse State Park showing the mileages to the Columbia River. 

There are four campgrounds along the trail, between Ollalie State Park and Kachess Lake. They have a few sites and a (nice) pit toilet. They are Roaring Creek, Cold Creek, Carter Creek and Alice Creek. Camping is also available near the trail at USFS camps at Tinkham, Lake Kachess, Denny Creek, and Crystal Springs. There is state park camping at Lake Easton and Wanapum. This map from along the trail highlights a few of the sites:

Heading east, about 20 miles from Cedar Falls, you will encounter the first of several tunnels, the Snoqualmie Pass Tunnel:

It's 2.3 miles long and open May 1 to Nov 1.  It's possible to detour around the tunnel when it's closed without riding on the I-90, but it's a much longer route - you leave the trail at FR 5510, follow back roads that parallel the freeway, and pick the trail back up at Hyak:

No matter which way you go, you'll end up at Hyak, which has a nice rest area and picnic tables.

Once past Hyak, you spend the next few miles along Keechelus Lake (aka Stump Lake) before reaching the next tunnel.

Important note: the trail conditions deteriorate the farther east you head. Once into central washington the gravel is much looser and there is sand due to a lot of equestrian use. Very wide tires are highly recommended. For an excellent summary of the route as of Labor Day 2013, see this two-part series on Bike Overnights (part 1, part 2), it has in-depth information on the trail conditions heading east. For another excellent summary of the full route, see this web page. Here's one from Oct 2015, very in-depth with plenty of photos. It really highlight how difficult this trail is once you get into the eastern part of the state.