Hi- thank you for your question about the possible whale bone you found on the beach. What an exciting find! I have consulted with William Hanshumaker of Oregon Sea Grant and James Rice of Oregon State University. They both believe it
is probably one of the uppermost vertebrae of a large "rorqual" whale. This family of
whales, the Balaenopteridae, include the Blue and Humpback whale species, and others. Unfortunately it is very difficult to identify the species from the one bone.
Jim is the coordinator for Oregon's Marine Mammal Stranding network, and if you contact him and let him know exactly where you found it, he should be able to tell you if there was a known stranded or buried whale in that area.
Here is a web site with some information about these whales.
Other than that, I know the Seymour Marine Discovery Center in Santa Cruz, California has Blue and a Gray whale skeletons on display: http://seymourcenter.ucsc.edu/exhibits/outdoor-giants/. If you can't visit, perhaps one of the lab's research scientists can ID the bone from your (very nice) photo.
Take care, and keep discovering!
Thank you for this information.