This truss structure is connected to steel girder ramps including the beginning of one on the east side to connect to the Mount Hood Freeway, which was never built. The bridge was designed economically with little public input and it's considered to be an eyesore. I think it's a perfectly normal looking three span truss bridge, but for some reason it upsets Portland sensibilities. Perhaps it's because it carries 136,000 vehicles a day into and out of the city. In any event, there are committees that come up with various schemes for removing this bridge that are never acted upon.
Portland's Bridges: Marquam Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.