A short and gentle day hike from Salmon la Sac, Cooper Lake is a great place to visit for a day of swimming or fishing. It is not necessary to make the trip on foot since it is also accessible by car, but if you do choose to hike you'll have a pleasant, ambling trek along the Cooper River.
From the Salmon la Sac Trailhead, start hiking along the river as the trail splits off from those heading to Polallie Ridge and Waptus Lake. With only 400 feet of elevation gain, the trail stays gentle throughout as it rolls along the river valley through old-growth trees, berries, and occasional patches of wildflowers. The river is full of plump trout, so keep an eye out for good fishing holes as you walk by.
After 3 miles the trail intersects Cooper Lake Road and continues on the other side just down the way. As the lake comes into view through the trees, the primitive campsites of Owhi Campground start appearing on either side of the trail. Access the beach from the campground for a good picnic spot, or continue on toward the boat ramp. Since no motorized boats are allowed on Cooper Lake, it is an ideal spot for swimming, kayaking and canoeing.