If I want to research on one, from the late/ mid 20th century. how far can I go? Are there any options? What agencies do you use? I’m interested in getting the “cause” given. Is this information lost?
Contact the county clerk of court where the divorce was filed in to see what is available.
The court records should still be on file at the courthouse where the divorce happened … that’s a start … note that some jurisdictions only allow “irreconcilable differences” as a cause … you may be able to find this information over the internet if you look up the laws where the divorced was filed …
My great-grandparents were divorced in 1910 and I was able to get all the court records and filings (ggm left ggf because he was a jerk, he sued her for divorce on the basis of abandonment, she got a small settlement, they both died broke 18 years later). Court clerk should have whatever is available.