I originally intended to ctb by jumping, but when I did further research I discovered that there don't appear to be any suitable locations in Washington or the greater Pacific Northwest. So I decided to investigate other methods and landed on nitrogen + exit bag instead, which was quick and easy to obtain without the risks and uncertainty of jumping from a suboptimal location.
I'm not aware of any natural cliffs in the area that are high enough to reliably ctb. You'd want over 300 ft minimum drop (see the
Jumping megathread) onto a hard surface to be confident of death.
There
may be cliffs that high somewhere in the mountains around here, but I'm not sure where and how to measure it to be sure it's high enough. Also, if the drop is not fully vertical you would end up smashing into the wall, mangling yourself on the way down with a good chance of finding yourself alive at the bottom in excrutiating pain. If anybody saw you a rescue team would be called, and you'd end up getting airlifted to the hospital, suffering in intense agony while racking up massive medical bills, with a very high chance of permanent disabilities in the end. There are so many ways that could go wrong, I absolutely do not recommend it.
There are several bridges in the Northwest that people have regularly jumped from, you can find news reports and search Reddit to find spots around Vancouver B.C., Seattle, and Portland. Suicide barriers have been installed on all the main bridges, though. There is a tall bridge at Deception Pass that has been used for suicides including recently, but it's only 180 ft drop into water. There is a good chance you'd survive the fall with shattered bones and drown in agony.
To get a sense of the height, the Golden Gate Bridge drop is 240 ft for comparison. Several people survived that jump and swam to shore or were rescued, and it's known that many (or most?) others survived the initial fall and ended up drowning, so you really wouldn't want to jump from anything lower.
Most of the high places I'm aware of are in the Seattle area, but there aren't any accessible spots that are tall enough, and the city has a high popluation density so you'd risk hurting someone if you tried. There are a few ~10 story parking garages downtown, which is barely tall enough, and there are constantly people on the sidewalks where you'd be landing. The Aurora bridge used to be a notorious suicide hotspot, but now there's a tall suicide barrier. People have ctb'd from the West Seattle bridge, but it's only 140 ft and you'd either land in water, or in the middle of an active seaport with significant risk of hurting someone.
I also considered going down to Portland, but it's basically the same situation as Seattle. There are parking garages and bridges, but they aren't tall enough and there will generally be a lot of people around. People certainly do ctb by jumping in those locations, but it's risky and I think you should look into other, safer options.