During WW II, the city of Portland commissioned Robert Moses, an urban planner form New York City, to plan the transportation system for the future. Moses and his team envisioned a central freeway ring around city (see diagram below). This central ring became the Marquam and Fremont bridges, I-5 (aka East Bank freeway) and I-405 (aka Stadium freeway). Thru the 1950's and 60's, highway planners expanded on this ring, creating the following freeways: the Mount Hood (Marquam bridge ghost ramps), the Rose City or Prescott freeway (east end of Fremont bridge ghost ramps), the Baldock (I-5 south), the Banfield (I-84), the Sunset freeway (US 26 thru the west hills tunnels), the Minnesota freeway (I-5 north), the St. Helens 505 Industrial freeway (Hwy 30) and other freeways that were never built. These never-to-be-built freeways led to the many ghost ramps in our city.
The picture below shows the Marquam bridge under construction in 1964.
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The Fremont bridge was completed in November of 1973.
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The diagram pictured below was taken from Robert Moses Portland plan published in 1943.