Action Comics #252 (1959)

In Action Comics #252, witness the historic first appearance of Supergirl in "The Supergirl from Krypton!" You'll be amazed as Superman's long-lost cousin arrives on Earth and begins to adopt a secret identity in order to help Superman in the never-ending fight for truth and justice. But that's not all - this issue also introduces the Menace of Metallo, as Superman faces off against one of his most dangerous foes yet. And as a special bonus, you'll also get to see Congorilla take on a small army of desperate men who want nothing more than to see Congo Bill die at dawn! This issue, with its incredible cover by Curt Swan and Stan Kaye, is not to be missed. So join us as we take pride in introducing...The Supergirl From Krypton!