Mercer Corridor Streetscape Design

Seattle, Washington

Project Size:

Gross area: 161 acres

Project Status:

Completed 2008


Civic Design, Transportation Design, Urban Design

The Mercer Corridor is a critical component in the transformation of Seattle’s South Lake Union neighborhood. Once a famously dysfunctional artifact of the 1962 World’s Fair and known for decades as the “Mercer Mess,” the 4-lane arterial is reinvented as a grand boulevard that laces together adjacent neighborhoods and provides a dramatic gateway to the city.


Program and Site
The project site consists of Mercer Street and Valley Street, straddling between dense commercial and residential street blocks to the south and the Lake Union waterfront to the north. A series of recent investments in the waterfront, including South Lake Union Park and the Museum of History and Industry, place the Mercer Corridor as a central bridging element connecting the rapidly growing neighborhood with cultural amenities and green space.


Working with a team of engineers and transportation planners, LMN developed key urban design concepts to guide the creation of a grand urban boulevard with influences from cities around the world. Working from a City decision to widen Mercer Street and change traffic flow from 1-way to 2-way, the design includes wide, pedestrian-friendly sidewalks, a planted median, large-scale trees, bold lighting and public art. The scale and character of the boulevard is appropriate to dense, mid-rise buildings, with strongly defined crossing zones, pockets of public space, and large-scale landscape expressions meaningful to passing cars. Artist Ellen Sollod collaborated with LMN on several aspects of the streetscape design, and her Origami Tessalation – a 28’ tall illuminated column located on the landscaped median of Mercer Street – symbolically marks entry to the area from Interstate 5.  Ellen’s work was commissioned by the Seattle Office of Arts and Culture with support from SDOT and City Light.


Valley Street—formerly the westbound counterpart to Mercer—is narrower and patterned after the Dutch “woonerf” concept, with traffic calming measures that make it comfortable for bikes and pedestrians as well as a streetcar line. On one side, the street interfaces directly with the park, while on the other, a heavily planted sidewalk and parking strip set the stage for vibrant streetfront retail and café seating.