Found an old dual sport bike, how to get a title?

[nsphelps2002]

So I was clearing some sticker bushes on family owned property and happened to find a Suzuki TS185 under about 10 feet of sticker bushes, it had a recreational tag on it that expired in Dec. '79. No one knows who's it is or how it got there, it is almost complete, and the property has been in the family since the 1930's. I live in Washington state and was wondering if there was and way I could get some sort of title for it.