Lake Easton State Park is not a wilderness park, but it is scenic and peaceful. You can put together a five-mile loop hike on the park trails and on a section of the Palouse to Cascades State Park Trail, if you don't mind walking on roads for a bit through the town of Easton. This hike makes for a good leg stretcher when you need a break from I-90.
Drive into the park entrance. Park in any of the day use areas along the lake. Follow the lakeshore trail southeast, cross a couple of park roads, pass the campground, and make your way onto the Riverside trail by the Yakima River.
Continue walking to the end of the Riverside trail, to where it comes out on Lake Easton Road, right by the Yakima River bridge.
For the loop, cross the road bridge and walk into Easton. A couple of businesses provide food and drink here. Walk through the town, a matter of a quarter mile or so, then turn right on Cabin Creek road and cross the Burlington Northern Santa Fe (BNSF) railroad tracks. Continue curving around to the northwest on Cabin Creek road to where the signed Palouse to Cascades trail takes off on the right hand side.
After half a mile this trail enters deep woods, with the railroad and Lake Easton on your right. A short tunnel from railroad days is along this stretch. The trail was once the Chicago, Milwaukee, St. Paul and Pacific transcontinental railroad, abandoned around 1980.
About 1.5 miles after getting on the Palouse to Cascades trail, cross the railroad tracks again on a gorgeous trail bridge that also spans the Yakima River. The rail trail continues for many miles, through Snoqualmie Pass and on to Rattlesnake Lake and beyond, but you turn right shortly after crossing the bridge.
Walk through the woods on the west side of Lake Easton, eventually arriving on a road (old US 10) close by I-90. Walk this road, using an old concrete bridge to cross an arm of the lake. This is the bridge you see while zooming past on I-90. Another mile of trail and road walking will take you back to your car.