The Supreme Court first declare gender-based classification unconstitutional in 1971 in Reed v Reed.
It was an equal protection case in which the Supreme Court ruled that the administrators of estates cannot be named in a way that discriminates between sexes.
The case was related to Sally and Cecil Reed, a couple who were separated and fought about which of them was going to be designated administrator of the estate after their son's death.
The Court struck down the Idaho law designating the male descendant as the administrator of the estate.