This article on Bend.com is interesting, about the occurence (and likelihood of) tsunamis off the coast of Oregon.

Some time between 9 and 10 p.m. on Jan. 26, 1700, a similar great earthquake, with the same estimated magnitude as the one in Asia, struck the Northwest, rocking the region with strong shaking for several minutes. The specific time can be told through a variety of evidence closely studied by scientists in recent years, such as land levels, sand deposits, the rings of ancient trees and historic records….

 

Geological evidence indicates that mega-quakes have occurred in the zone at least seven times over the past 3,500 years, meaning they happen, on average, every 400 to 600 years.

With a little digging, I found out this was the Cascadia Earthquake (thank you, Wikipedia), a magnitude 9 megathrust earthquake that slammed the Pacific Northwest. I also found this page which has a somewhat more consequential description:

The earthquake collapsed houses of the Cowichan people on Vancouver Island and caused numerous landslides. The shaking was so violent that people could not stand and so prolonged that it made them sick. On the west coast of Vancouver Island, the tsunami destroyed the winter village of the Pachena Bay people, leaving no survivors. These events are recorded in the oral traditions of the First Nations people on Vancouver Island.

Freaky. I knew the area was geologically active—volcanoes and such—but I had no idea it was this active.