The Klondike Swamp Trail traverses much of what is special about Cougar Mountain Park, utilizing old logging roads and railroad grades that take you through charming second growth forest. The loop is easily accessed from the Sky Country Trailhead in Bellevue, and offers a nearly level grade for most of the journey. In general, trails here are maintained to high standards. This is a favorite area for runners and dog walkers. Please note that bicycles are not allowed on park trails.
Klondike Swamp is most easily reached from the southern edge of the parking area. There you'll see a kiosk with information about the park and some history on the nearby Nike Launch area, which was used during the Cold War as a defense station. Other kiosks along the way tell the story of logging and mining with excellent photographs accompanying the text.
The hike begins on the Old Man's Trail (C11), beyond the kiosk, and proceeds to an old road with a sign marking that the hike goes right. The former missile launch site appears on the right as a large and empty field. Another sign marks the beginning of true trail, which enters a recovering forest of mixed trees. Many species thrive here, including Douglas fir, western hemlock, western redcedar, silver fir, and Sitka spruce, but alder predominates.
At 0.25 mile a couple of mine holes that hold water in wet months are marked by barricades and a warning about trespassing. Skunk cabbage fills the low, swampy areas, bringing color to the scene in spring. The sides of the trail are decorated with trillium that range from white to pink to dark purple. The trail then passes a stile and proceeds to the right, following Cave Hole Trail (C3) downhill to a junction with the By Pass Trail (C9).
Turn left onto C9 and cross the outlet of Klondike Swamp at 0.5 mile. The stream is surrounded by a cedar forest with an understory of sword fern and vanilla leaf. A low profile switchback entertains the notion of climbing but the trail quickly levels upon meeting Fred's Railroad Trail (C7). Turn left and soon cross the Clay Pit Road at a junction with a kiosk that offers some history on logging at Cougar Mountain.
Follow the Klondike Swamp Trail (N5) beyond the kiosk, passing stumps of ancient Douglas fir that now support second growth hemlock. Their rotting remains hint to the hiker of the magnificent forest that once stood here. Moss laden vine maples and alder trunks festooned with licorice fern line the trail as you pass the swamp's southern margin.
Stay left on N5 at a junction and proceed along the east side of Klondike Swamp. Views into the swamp are generally obscured by trees and thickets of riparian vegetation in warmer months. Several Sitka spruce betray the boundary of the wetland and indicate a rich ecosystem that is recovering after complete deforestation.
Stay left again at the next junction and cross over the inlet of Klondike Swamp at 1.5 miles. Just beyond and uphill is a T junction with the Coyote Creek Trail (N4). Turn left and follow the western edge of Klondike Swamp before heading gently uphill and away from the swamp.
N4 twists and turns through a mixed forest, gaining and losing a small incline before coming upon Clay Pit Road once again at 2.2 miles. Turn right onto the road for a short walk back to the Sky Country Trailhead or proceed straight across the road on C3 and then turn right onto C11 for a slightly longer finish.