How far back does a title search go?

A typical "title search" or abstract goes back 50 years. I am unaware of a regulation or mandate which requires a specific # of years, but a prudent title searcher would certainly go back as far as possible if there is some sort of ambiguity or question. Generally, the complexity of the matter would be represented in the fee charged to you since the title insurer bears the risk of insuring your property and they would certainly not take a chance for you or themselves.