Milepost 31 highlights the people and projects that shaped Pioneer Square and provides an inside look at the SR 99 Tunnel Project.
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Visitors to Milepost 31 will find more than just construction photos and brochures. You’ll find history, artifacts and interactive exhibits designed to broaden your understanding of the land beneath you. You’ll explore the neighborhood’s changing landscape, from earth-moving efforts of the past to the massive tunnel project that will soon move State Route 99 underground and reconnect Pioneer Square to the waterfront.
Visitors can browse through four sections:
- You are here: Similar to the “you are here” points on maps, this section orients visitors to Milepost 31. It tells the story of the land upon which you are standing from the perspective of several different historical figures.
- Moving Land: This section examines how the natural forces of glaciers, earthquakes and volcanoes have transformed Seattle’s landscape during the past 15,000 years. Visitors will also learn about our own effects on the land, from the filling of the tidelands in Pioneer Square to the various regrade projects across the city.
- Moving People: This section tracks transportation over time, with an emphasis on Pioneer Square. Visitors will see how people-moving has changed – and in some cases stayed the same.
- Moving Forward: This section is all about tunneling. Visitors will learn about the history of tunneling technology, tunneling in Seattle and, of course, the SR 99 Tunnel Project. In addition, exhibits show visitors how the project – along with the Elliott Bay Seawall Replacement and Waterfront Seattle – will transform the future of Pioneer Square.
|Where to find us
Milepost 31 is located at 211 First Ave. S. (between South Washington and South Main streets) in Seattle.
Why create Milepost 31?
This information center is required by a memorandum of agreement (pdf 510 kb) signed as part of the Alaskan Way Viaduct Replacement Project. The agreement was developed to address Section 106 of the National Historic Preservation Act, which requires agencies to take into account the effects of their projects on historic properties, such as those in the Pioneer Square Historic District.
Within the agreement, city and state preservation officers along with the Federal Highway Administration, national and local preservation groups, neighborhood organizations and local tribes determined that a project information center is one way WSDOT could help to keep Pioneer Square vital during construction. The agreement also calls for WSDOT to monitor and protect historic buildings during SR 99 tunnel construction and to develop traffic management and construction coordination plans for Pioneer Square.
Why the name “Milepost 31”?
Mileposts mark progress. They help you track where you are on your journey, reminding you of the places you’ve passed through on your way to somewhere else.
But what if a milepost is so interesting that it becomes a destination? Located on SR 99 at the western edge of Pioneer Square, Milepost 31 is that kind of place. It marks a spot on the highway, but it also marks the spot where, before mileposts existed, mile-thick glaciers gave way to native civilizations. It’s where Seattle’s first neighborhood saw the rise of the city’s most notorious stretch of highway – the SR 99 Alaskan Way Viaduct – and where crews building the world’s largest diameter bored tunnel to replace the viaduct will first cross into the soils beneath Pioneer Square.
211 First Ave. S., Seattle (between South Washington and South Main streets)
Admission is free. Tues-Sat 11am-5pm