Welcome to a virtual tour of Milepost 31, the SR 99 Tunnel Project’s public information center!

Milepost 31 was located in Seattle's Pioneer Square Historic District from December 2011 to November 2017. The center provided an inside look at the history of the neighborhood and the engineering behind the SR 99 tunnel. It was created as part of an agreement 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 neighborhood.

Start the tour above or jump to a section in the exhibit at one of the thumbnails below. You can also check out a couple of videos at the bottom of the page.