All we were ever told is that she died and that was told us on the pilot for "The Andy Griffith Show" which appeared on "The Danny Thomas Show". Opie's pet turtle , Wilford, was stepped on and killed by "Mrs. Balford" out in front of the ice cream parlor and he wants Andy to arrest her for 'murder', give her a fair trial and "hang her." Andy tries to help Opie deal with the loss by talking about how it was when Opie's 'ma' died. Opie looks to Andy and says, "Who stepped on Ma?" That was the only time Andy's first wife was mentioned.
Besides the pilot, she is also mentioned in "Wedding Bells for Aunt Bee." Opie asks Andy, "Did you and Ma have that kind of love?" Andy replies, "Yes, son, we did."
We never do learn her name, or anything else about her, but there are a few hints here and there.
In the pilot episode, Andy reminds Opie, "I lost your mom when you was just the least little speck of a baby." Of course, there are lots of things in the pilot episode that changed before the first episode, but I'd consider
this official since it established from the very beginning that Andy was a widower raising a boy, and that never changed throughout the entire series.
Therefore, Opie never knew his mother. Perhaps she died giving birth. Andy might have meant something else by "lost," but I doubt it. It would have been unthinkable for a woman to "run off" from a good man like Sheriff
We also learn in other episodes that Barney was Andy's best man (he says "I stood up for you when you first got married," which I assume means he was best man), and that Barney is Opie's Godfather. I suppose it is possible
that Andy had been married twice (before Helen came along), but there's no evidence to suggest this.
- Added by Paul Mulik