Robert Moses via Wikimedia
Being a Portland native I have always been familiar with the Interstate freeways. Robert Moses, a 'Master Builder', was brought to Portland in the early 1940's and planned what was to become I-205, I-84, I-5, I-405, and Highway 26 (via Mercury). These are freeways almost every Portlander is familiar with. In 1956 Congress created the Federal-Aid Highway Act that would cover 90% of the cost. Automobiles took over and Portlands last Electric car closed in 1958 which was the same year Portland's first freeway was finished. While these freeways prove useful, many roadways in Portland have faced an early demise.
Harbor Drive via Vintage Portland
The first of these is Harbor Drive which ran along the west waterfront in downtown Portland. Harbor Drive was removed and became what is now Tom McCall Waterfront Park.
Houses were demolished in SE Portland near Division and 27th to make room for a freeway. This plan was scrapped and the land became Piccola Park.
I5s Ramp to Nowhere via Jason Kinney
Just north of Burnside where I5 joins up with I84 there are two ramps that lead to nowhere. A possible indicator of a planned road that never came to be.
Proposed Waterfront Development 1932 via cafeunknown.com
This image from a 1932 Proposal shows a Portland that looks more similar to today than it did 40 years ago. A waterfront park can be seen on the west side of the Willamette river despite Harbor Drive being built 11 years later.