What precise historical information must be disclosed to a potential spouse in order to validly marry (i.e., not be married under false pretenses) is, I think, quite minimal.
One must not know every single thing about an individual's past in order to validly marry that individual. On the other hand, anything that would have a substantial affect upon the prospective spouse (e.g., a criminal past that may preclude future employment, large debt that may be taken into the marriage, venereal diseases contracted and other known medical problems that would affect the potential spouse, prior religious beliefs and affiliations if one is a convert, etc.) must be, I think, disclosed. Most of these type of past issues would, over the course of a friendship (which I think is important in a successful marriage) would probably come up in conversation over the course of time.
In any event, if there is anything a partner wants to keep hidden, it is probably important enough to disclose though would not ordinarily invalidate a marriage.
Specific questions should be discussed with your confessor.
If you want to take Novus Ordo standards, however, I think if you, or anyone you know, has ever had a hangnail during any time you've known the potential spouse, you would probably have grounds for an annulment even if you didn't know about it.