"The Supergirl from Krypton!" debuted in Action Comics #252 (May 1959). The character was created by writer Otto Binder and artist Al Plastino. Kara Zor-El is the paternal cousin of Kal-El from Argo City on Krypton. The city survived the destruction of the planet, but became irradiated with kryptonite. Fifteen-year-old Kara was rocketed away to Earth by her parents, Zor-El and Alura In-Ze. Superman places Kara in Midvale Orphanage to protect and mentor her. She chooses the secret identity of Linda Lee and disguises herself with a pigtailed brunette wig.

Detective Comics produced a copyright ashcan for a Superwoman title in late 1941, and a Supergirl title in 1944. Both names have been used by various DC characters over the years, beginning with Action Comics #60 (May 1943). In the story "Lois Lane -- Superwoman!" by Jerry Siegel and George Roussos, Lois dreams that she has superpowers after receiving a blood transfusion from Superman. In Action Comics #156 (May 1951), Lois dons a blonde wig as Superwoman. In Superboy #5 (November–⁠December 1949), Superboy helps Queen Lucy of Borgonia pretend to be "Supergirl." In Superman #123 (August 1958), Jimmy Olsen uses a magic gem to wish a "Super-Girl" into existence.

Kara Zor-El first appeared in DC advertisements during the spring of 1959. According to Al Plastino, the only discussion was, "Should she be blonde?"

 

Superman creator Jerry Siegel returned to DC Comics in 1959 and contributed Supergirl stories for Action Comics throughout the 1960s. The first Super-Pet companion of Supergirl, Streaky the Supercat, was created by Jerry and artist Jim Mooney. In Action Comics #261 (February, 1960), a stray cat is accidentally exposed to X-Kryptonite and given temporary superpowers. Comet the Super-Horse was created by Jerry and artist Curt Swan, first appearing in Adventure Comics #293 (October 1962). Comet was an ancient centaur transformed into an immortal horse. Comet and Supergirl first meet in Action Comics #293 (September 1962).

Supergirl meets the Legion of Super-Heroes in Action Comics #267 (August 1960). Red kryptonite temporarily ages Supergirl into a "Superwoman" and she is unable to join due to the 18-year-old age limit. Supergirl encounters the Legion again in Action Comics #276 (May 1961). After Brainiac 5 helps Supergirl pass the trials, both are chosen to become Legionnaires. They develop feelings for each other, but Supergirl leaves the 30th century to continue assisting Superman.

In Action Comics #273 (February 1961), editor Mort Weisinger asked readers to "Pick a new hair style for Linda (Supergirl) Lee!" The "Campus Cuddle-Bun" received 10,112 of the 20,477 votes, officially appearing in Action Comics #281 (October 1961). The hairstyles were designed by Jim Mooney.

Superman would not allow Supergirl to be adopted from the orphanage, fearing that she would expose her identity. Since her arrival, Kara was forced to operate as a "secret weapon" for Superman. The plots often limited her power usage away from the public eye. In Action Comics #279 (July 1961), 16-year-old Kara is adopted from Midvale by Fred and Edna Danvers. She takes their surname, becoming Linda Lee Danvers. After proving herself to Superman, Supergirl is formally introduced to the world in Action Comics #285 (February 1962).

 A new costume was revealed in Adventure Comics #397 (September 1970). The outfit was assembled by Diana Prince based on designs submitted by readers Louise Ann Kelly and Jean Bray. Different variations were worn over the next two years including a swimsuit designed by Margret Berg in issue #409 (August 1971). The most recognizable Supergirl uniform of the era is the balloon sleeve blouse and hotpants designed by John Sposato, first appearing in issue #410 (September 1971).

The Supergirl logo was redesigned by Gaspar Saladino for the cover of Adventure Comics #398 (October 1970). A solo Supergirl title was published for ten issues from November 1972 to October 1974. After quitting her job at KSF-TV in San Francisco, Linda Danvers enrolls in the School of Drama at Vandyre University.

Superman's Pal, Jimmy Olsen, Superman's Girlfriend, Lois Lane, and Supergirl were combined into The Superman Family beginning with Jimmy Olsen issue #164 (April–⁠May 1974). The Superman Family was published for 59 issues until September 1982.

The Daring New Adventures of Supergirl debuted in November 1982. The original series logo was designed by Todd Klein. Linda Danvers moved to Chicago and studied psychology at Lake Shore University. A new uniform was introduced in issue #13, retitled Supergirl for the remainder of the series. In issue #17 (March 1984), Supergirl added a headband as a "symbol of citizenship on Krypton!" The updated look was used in screen tests for the 1984 film Supergirl starring Helen Slater.

 

Power Girl debuted in All-Star Comics #58 (February 1976). Power Girl was originally Kara Zor-L, the cousin of Superman on Earth-Two. In the multiverse, Earth-Two includes characters from the Golden Age of DC Comics. Power Girl was rocketed from Krypton, remaining in stasis before arriving as a woman in her twenties. Power Girl survived the destruction of Earth-Two during the "Crisis on Infinite Earths" event and her origin would be retconned over the years.

Supergirl of Earth-One was killed battling the Anti-Monitor in Crisis On Infinite Earths #7 (October 1985). Her body is brought to the Fortress of Solitude before being placed in orbit on the opposite side of the Moon. Superman later delivers Kara to her Kryptonian parents in Superman #414 (December 1985). After the defeat of the Anti-Monitor, the multiverse worlds were merged into New Earth.

The "Crisis on Infinite Earths" led to continuity problems for Legion of Super-Heroes stories in the 30th and 31st centuries. On New Earth, Superman never became Superboy and Supergirl never existed. Kal-El remembers Superboy-Prime and elements of the Crisis, but Kara is seemingly forgotten. The Time Trapper created a Pocket Universe containing a copy of Krypton and Earth-One. The Superboy of the Pocket Universe died saving the Legion, leaving Earth unprotected from the Phantom Zone criminals.

The Pocket Universe Lex Luthor created a superpowered being named Matrix. Matrix has super-strength and the power of flight plus telekinesis, invisibility, and shapeshifting abilities. The character was created by writer Roger Stern, first appearing in Superman vol. 2, #16 (April 1988). Matrix is first referred to as "Supergirl" in The Adventures of Superman #441 (June 1988).

Matrix assumes the role of Supergirl on New Earth and she is nicknamed "Mae" by the Kents. Matrix becomes romantically involved with Alexander Luthor II, the clone disguise of Lex Luthor on New Earth. A one-shot Supergirl and Team Luthor (April 1993) was released during the "Funeral for a Friend" storyline following the death of Superman. Matrix appeared as Supergirl in a four-issue Supergirl miniseries dated February 1994 to May 1994.

 

Writer Peter David rebooted the character, introducing Linda Danvers of New Earth in Supergirl vol. 4, #1 (September 1996). Linda lives in Leesburg, a reference to Linda Lee Danvers. Linda and Matrix merge to create a new Supergirl. In issue #51 (December 2000), Linda assembles a new costume based on the 1998 design of Kara In-Ze in Superman: The Animated Series.

The Pre-Crisis Kara Zor-El returned in the six-part series finale "Supergirl: Many Happy Returns" in issues #75–⁠80 (December 2002–May ⁠2003). In order to prevent the events of Crisis on Infinite Earths, Linda travels backwards in time to replace Kara on Earth-One. Linda marries the Superman of Earth-One and they have a daughter named Ariella Kent.

 

Kara Zor-El of New Earth first appeared in Superman/Batman #8 (May 2004). Kara is the paternal cousin of Superman, sent from Argo City to escape an attack from Brainiac. Kara takes the secret identity of Linda Lang, the foster niece of Lana Lang. The character was featured in Supergirl vol. 5 from October 2005 to October 2011.

 Following the events of "Infinite Crisis," Kara became a Legionnaire in the 31st century. Legion of Super-Heroes vol. 5 was renamed Supergirl and the Legion of Super-Heroes for issues #16–⁠36 (May 2006–⁠January 2008).