Mercer Slough Nature Park | Belleville

Mercer Slough Nature Park is one of the largest remaining freshwater wetland ecosystems in the Puget Sound region, encompassing over 320 acres in the heart of Bellevue, Washington. It offers a rare and harmonious blend of natural beauty, environmental education, and low-impact outdoor recreation. Situated just south of downtown Bellevue, it serves as an ecological sanctuary in the midst of a bustling urban environment.

Ecological Significance

Mercer Slough is a slow-moving waterway that drains into Lake Washington. The park consists of a rich mosaic of ecosystems, including marshes, swamps, wet meadows, riparian corridors, and forested uplands. These habitats support over 170 species of wildlife and more than 300 native plant varieties.

The slough plays a critical role in water filtration and flood control. Wetland vegetation filters pollutants from urban runoff before they reach Lake Washington, helping to maintain water quality. The dense root systems of native plants also stabilize the soil and reduce erosion.

Key species found here include great blue herons, river otters, beavers, red-winged blackbirds, garter snakes, Pacific tree frogs, woodpeckers, and bald eagles. The biodiversity makes the park a prime location for birdwatching and wildlife observation throughout the year.

Trail System

Mercer Slough Nature Park features over 7 miles of trails, including gravel paths, paved multi-use trails, and raised wooden boardwalks. These trails are well-integrated with Bellevue’s wider trail network and vary in length and character, offering accessible experiences for all fitness levels.

Bellefields Loop Trail (0.8 miles): Begins near the Environmental Education Center and loops through wetland forest on boardwalks. It's shaded, flat, and full of interpretive signage about plant life and wetland ecology.

Heritage Loop Trail (1.1 miles): Circles through open meadows, a historic blueberry farm, and forested groves. This trail passes the historic Winters House and connects with other loops for a longer walk.

Periphery Trail (~4 miles): A paved loop used by walkers, runners, and cyclists. It borders the park and links with the I-90 Trail, making it ideal for commuters or longer recreational circuits.

The trails are interconnected and provide many options for short strolls or longer explorations. Many areas include benches, viewing platforms, and quiet spots for reflection.

Water Trail

The slough’s 2.6-mile canoe route is a unique feature that allows visitors to experience the wetlands from a different perspective. The water trail begins at Enatai Beach Park, where canoe and kayak rentals are available during warmer months.

The water route winds northward through calm, tree-lined channels, past lily pads, reed beds, and open water.

It’s a no-motor zone, ensuring a quiet paddle with chances to spot beavers, turtles, and herons up close.

Interpretive markers along the route identify ecological zones and offer educational information.

City-sponsored ranger-led canoe tours operate from Memorial Day through Labor Day, combining naturalist commentary with hands-on experience.

Mercer Slough Environmental Education Center (MSEEC)

This LEED-certified facility is operated in partnership with the Pacific Science Center. It includes several modern buildings elevated on stilts and connected by wooden walkways to preserve the wetlands below. The architecture blends into the environment and is designed to be ecologically responsible.

Features include:

Visitor center with interpretive displays about the wetland ecosystem

Classrooms for school and community programs

Community meeting spaces

Treehouse-style overlook deck with panoramic views of the slough

Restrooms, water fountains, and picnic areas

Programs at the center include nature camps for children, seasonal workshops, ranger-led nature walks, art-in-nature classes, and conservation seminars.

Historic Winters House

Located along the west side of the park near Bellevue Way, the Winters House is a 1929 Mission Revival-style home that once belonged to flower growers Frederick and Cecilia Winters. It is the only building in Bellevue listed on the National Register of Historic Places.

Today, it serves as a small interpretive center and trailhead. The house is surrounded by manicured gardens and often used for special events, small weddings, or as a serene entry point for exploring the slough. It offers historical context for the area’s agricultural roots and early settlement.

Blueberry Farm

An operational remnant of Bellevue’s agricultural past, the blueberry farm within Mercer Slough offers seasonal U-pick opportunities. From mid-summer through early fall, visitors can pick their own organic blueberries or buy pre-picked containers at the small farm stand. The fields are typically open from late June through August, depending on the crop.

The farm area is integrated with the trail system and serves as a peaceful, sunlit clearing in contrast to the shaded wetlands. It’s also a popular spot for photographers during bloom season.

Amenities and Visitor Experience

Accessibility:
The park is highly accessible, with ADA-compliant boardwalks, gentle paved trails, wide paths, and clear signage. Both the Environmental Education Center and Winters House have accessible parking and restrooms.

Parking:
There are five main parking lots around the park, including:

Environmental Education Center lot (off SE 16th St)

Winters House (along Bellevue Way SE)

Blueberry Farm parking

Bellefields Trailhead (south access)

Sweyolocken Boat Launch (for water trail users)

Safety and Cleanliness:
Mercer Slough is considered very safe. Park rangers and local police occasionally patrol the area, especially near the education center and Winters House. The park is well-maintained with clean restrooms and no entrance fee. Dogs are allowed on leashes, and waste stations are provided.

Events and Activities

Throughout the year, the park hosts various seasonal events:

Guided birdwatching walks in spring and fall

Salmon viewing tours during spawning season

Wetland ecology workshops for families and educators

Canoe adventures for both beginners and experienced paddlers

Blueberry harvest events with live music and family activities

The blend of recreation, education, and conservation makes Mercer Slough not just a park, but a living classroom and urban refuge.

Unique Value

Mercer Slough Nature Park offers something few urban parks can: complete immersion in a living wetland ecosystem without leaving the city. Whether walking among cattails and towering ferns, gliding silently through still waters, picking blueberries on a summer morning, or learning about ecology from a naturalist, the experience is both grounding and enriching.

It is a place of quiet discovery, where the rhythm of nature persists just beyond the hum of city life. For residents, educators, and nature-lovers alike, it’s an invaluable environmental and cultural resource in the heart of Bellevue.