Mercer Slough

Kelsey Creek collects in the Lake Hills greenbelt wetlands between Phantom Lake and Larsen Lake, crosses Bellevue's Crossroads neighborhood and Kelsey Creek Park, then turns west, becoming the Mercer Slough just beyond Interstate 405 [1]. At 367 acres, the slough is the centerpiece of the largest wetland beside Lake Washington, and it meets that lake's East Channel at Interstate 90 [1]. The Duwamish kept a small outpost called Satskal along it [1]. For centuries these wetlands were swamp, marsh and shallow water, the slough little more than a shallow inlet of the lake [1]. In 1894 a small sawmill ran at the slough's upper end, floating logs and cut timber down to Lake Washington, and the water then carried vessels of several kinds, from rafts to tugs [1]. Once the Lake Washington Ship Canal and Chittenden Locks were done in 1917, the lake fell 8.8 feet, laying bare lake bed along the course the slough follows, and dredging in the 1920s made it passable for small craft [1]. King County and Bellevue started buying parcels there in 1957, holding 311 acres by 1990 [1].