There was something like a 7 year rule. A spouse disappearing and not been heard of at all for 7 years could be declared dead. It would need a court to make it formal, but I don't know if people would have bothered (the cost).
Whether formally declared dead or not, the woman would probably state she was a widow.
If a marriage would have been dissolved it might tell you on the marriage cert. I have one of 1948 worded like that: the bride is "the divorced wife of ...".