Coastline is a hard thing to measure, but Oregon has a lot of it. There are hundreds of miles of Pacific Ocean sea shore from the California border to Washington. The wide, twisty Columbia River adds several hundred miles extra of beach and shore, and even the smaller Willamette is a large river by most standards. But surprisingly, with all this shore, and with all the attendant islands, Oregon has few true, inhabited, unbridged islands. Sauvie Island is large by size, and is moderately populated, while the smaller Hayden Island is heavily populated. But both of those places are connected by road.
As far as I can tell, Oregon's only inhabited island that is only accessible by water is Eighteen Mile Island, a rectangular, rocky, 10 acre island in the Columbia River, between Hood River, Oregon and Mosier, Oregon. Since the island is between the Bonneville Dam and The Dalles Dam, its current size is probably stabilized, with its "natural" size fluctuating over a wider range with shifts in river, although apparently the island has been there a long time, with the Lewis & Clark Expedition perhaps making mention of it. Currently, the island is home to a single vacation home, and is only sporadically occupied.
I find the island most interesting because I would have thought, before researching the matter, that Oregon would have, at some point, more inhabited islands. With its diverse terrain and many isolated locations, it seems that Oregon would have several true islands tucked away somewhere. But apparently, this single house on a rock, a few hundred feet from shore, is Oregon's only inhabited, non-bridged island.