Introduced in the spring of 1959 by writer Otto Binder and artist Curt Swan, Supergirl is a female counterpart to Superman whose popularity and recognizability often rivals that of fellow superheroine Wonder Woman. The warm reception the character received prompted DC Comics to give the character a starring role in the back-up stories in Action Comics and by the late 1960s she had become the main feature of Adventure Comics.
Even though Superman's home planet Krypton was destroyed, one of its cities lived on. Encased by a protective force bubble, Argo City drifted through space for several years after the destruction of Krypton. One of its inhabitants was the brilliant scientist Zor-El, the brother of Jor-El and the uncle of Kal-El. When a meteor shower broke through Argo City's barrier and pierced its lead lining, the remaining Kryptonians began to die from radiation poisoning. Zor-El sent his only daughter, Kara Zor-El, to Earth where he trusted her superheroic cousin Superman would help raise her.
At the age of 15, Kara arrived on Earth and was promptly discovered by her cousin. Superman decided to use Kara as his "secret weapon" and encouraged her to hide her identity until the time was right for her debut. She was placed in the care of the Midvale Orphanage under the secret identity of Linda Lee. For a time, Kara covertly helped many people in Midvale with her superpowers and recurring narratives saw her sabotaging any plans made for her to be adopted due to her fear of her true identity being discovered. Eventually, Superman deemed Kara ready and introduced her to the world as his super powered cousin Supergirl. She was subsequently adopted by Fred and Edna Danvers, becoming Linda Lee Danvers in the process. Soon after she discovered her biological parents were still alive as they had teleported out of Argo City before they could succumb to the poisoning. Ultimately, Zor-El and Allura decide to stay in the bottle city of Kandor in order to give Kara as normal a life as possible.
Her most prominent foe during this era was the diabolical scientist Lesla-Larr who frequently escaped from Kandor to enact her various schemes against Supergirl. Another enemy of Supergirl's was the alien femme fatale known as the Black Flame. Supergirl also clashed with Superman's villains Lex Luthor, Brainiac and Mr. Mxyzptlk. Recurring plot lines often saw Supergirl in melodramatic ill-fated love stories with alien boys, suffering through ego-testing instances where the public turns against her and various narratives where her powers are either altered or removed altogether. Upon graduating high school, Kara secures a scholarship and attends Stanhope College as Linda Danvers. During this time, many of her stories revolved around her constant struggle to guard her secret identity. Supergirl's supporting cast continued to grow as well. She was sometimes aided by her pet cat Streaky and the centaur-turned-superhorse Comet. She was also inducted into the Legion of Super-Heroes and enjoyed casual relationships with Jerro the merboy and Dick Malverne, a boy from her old orphanage. For a time, Kara's best friend was Lena Thorul. Lena possessed ESP but ironically never knew that she was really the sister of Lex Luthor. Eventually, Lena moved away to start a family and Kara made other friends at college. As Supergirl, Kara had also befriended the vigilante known as Batgirl and the two worked together on a number of assignments.
Supergirl's first ever costume was a fairly straight-forward feminized version of Superman's costume. It was a blue dress with the Super insignia on the chest and was accented with a hip-length cape and a yellow belt. She completed the look with a pair of boots identical to Superman's. She kept her hair cropped short. The bangs often curled into a "C" shape and the hair itself was weighted with curls above the shoulders. As the 1960s drew to a close, Kara styled her hair in a flip style that was popular at that time. As Linda Lee, Kara wore a brown wig that she styled in pigtails and often wore Little House on the Prairie-esque outfits. Once she grew older, Kara ditched the pigtails for a flipped hairstyle with a headband and began dressing more fashionably.