I-505 was never built in Portland, but it still effected large parts of NW Portland in ways that can still easily be seen in the form of ghost ramps and other remnants. Many condos and other such properties have been built on land that was sat on for a while in anticipation of the freeway.
All pictures taken by me, 2009.
Fortunately, Portland came to it's senses before it was built, and instead routed the route along NW Yeon/US-30 instead of NW St Helens via NW Thurman/Vaughn as had been planned. The 1966 Comprehensive Plan shows it extending along this path, for example. This link has more information about Portland's planning past.
The Interstate Mileage was returned to the national system, and US-30 got a reasonable path that doesn't destroy any neighborhoods and still serves regional needs. The US-30 approach ramps to I-405/the Fremont Bridge are the most obvious legacy portions of the roadway other than the ramp stubs on the way to NW Vaughn/Yeon.
Good thing Portland thought things out, or else we'd probably not have this city we have now. I'll take a streetcar over a freeway through what's now my apartment any day.