Before the 1970s, a wife who wanted out of a bad marriage faced a legal gauntlet designed, in practice, to keep her in it. She had to prove her husband had committed a specific wrong: adultery, cruelty, or abandonment. If she couldn't, or if both spouses shared blame, the court could deny the divorce altogether. Until the late 1960s, divorce laws required the petitioning party to prove fault to obtain a divorce, and a person could not divorce their spouse merely because they were unhappy. That system didn't prevent marital misery. It prevented exits from it.
