how do i find out if my father's lawsuit for asbestos illness was settled? He passed in 1991 in Tulsa Oklahoma.

I am a lawyer in CT and practice in this area of the law.  You need to find out what state the lawsuit was pending in.  Then you can go to the judicial website and look up your dad's name as it should come up by a simple search.  If you know who your dad's lawyer you can try to call him and ask what if any the status is.  If an estate was opended in the town he passed away in, there may be an executor that would know.  You can finding this out by going to the probate court or calling the clerk there. Other than this I am not aware of any way to find out the answer.