Selina Kyle, who grew up to be the Catwoman, was born in 1920 in an undisclosed locale.  Little is known of the life of Selina Kyle before her marriage at 17 to a wealthy, but abusive, Gotham businessman.  Tiring of her physical and mental mistreatment, Selina quickly divorced her husband in 1938 but he was vengeful and ruined her financially and emotionally for her betrayal.  To get back at him (and obtain some needed resources), she broke into her former home and stole the gems he had bought for her but taken back, cracking a complex safe to do so.  In addition to recovering in gems, she got a thrill from doing it and learning she could do it led to her assuming the identity of Gotham's most famous cat-burglar (Revealed in Brave and the Bold #197).

    For two years, Selina operated under the name "The Cat", targeting wealthy individuals in her new identity.  One such target was wealth socialite Martha Travers, who was hosting an elegant yacht party to show off her $500K emerald bracelet.  Disguised as elderly Miss Peggs, the doddery acquaintance of Traver's nephew Denny, the Cat joined the party and coordinate the theft of the necklace with Denny.  Robin, sent by Batman to disguise himself as a steward, investigated the case and implicated Denny but was interrupted by the arrival of other crooks disguised as the coast guard.  Batman arrived soon after and the two defeated the crooks and recover most of the loot but not the necklace.  At the ball that night, Batman returned the goods stolen by the crooks but the necklace is not among them.  Robin sets off the fire alarm as a distraction and Batman notices Miss Peggs suddenly running like a much younger woman and pursues her.  There he has his first meeting with Selina Kyle who has the necklace taped to her ankle.  They return the emeralds and take the Cat into custody, but as they are heading back to shore, Batman, obviously smitten with the thief, allows her to escape (Batman #1).

Weeks later, while Batman is following up on the recent escape of the Joker, he finds the Cat (sometimes being called Catwoman, which will become her eventual nom du crime) on the Joker's trail as they are both pursuing the same prize, the Pharaoh Gem owned by E.S. Arthur. Batman catches Catwoman after she spies and she tells her what she knows of Joker's plans in exchange for her freedom.  When she, the Joker and  the Batman converge on the Arthur Castle, a three-way contest emerged in which Selina gets her hands on the gems first but seeing Joker about to kill Robin, offers them to him in exchange for the boy's life. Batman arrives and thrashes the Joker, leaving him to die as the castle catches fire.  He snags Catwoman as they depart but she leaps into the water and escapes (Batman #2).  Shortly thereafter, Selina adopted a cat mask to fill out her role as a costumed criminal when she was hired to steal diamonds in an internecine plot among a diamond syndicate but when Batman breaks it up, she escaped again (Batman #3).  She was shortly thereafter hired by Ian Karkull as part of a scheme to murder future Presidents but she could not complete her mission as while she was an accomplished thief, she never committed murder (All-Star Squadron Annual #3). Months later, she adopted yet another costume as she masqueraded as a wealthy socialite sending her guests (along with her thugs disguised as Batman) on a criminal scavenger hunt. As always, she was thwarted by Batman but escaped with a kiss (Batman #10).