On the ill-fated planet Krypton, Zor-El is the greatest scientist in Argo City, and the creator of a weather-proof plastic dome that covers the city. When the planet explodes, Argo is hurled into space in one piece, with its atmosphere kept intact by the dome. A few years later, Zor-El and his wife Alura give birth to their daughter, Kara.

When the ground beneath the city turns to deadly Anti-Kryptonite, a floor of sheet lead is laid to protect the people. However, when Kara is 15, a meteor shower strikes the city. The dome is of self-sealing plastic, but the lead is punctured, releasing the Anti-Kryptonite rays and dooming the population.

Having discovered Superman's presence on Earth, Zor-El and Alura use a small rocket to send Kara there, to be united with her cousin. Her mother has made a costume for her-the first of many different outfits she will wear during her career-similar to her famous cousin's.

Superman takes her to the Midvale Orphanage, where she disguises herself with a brown wig and uses the name Linda Lee. At first she is the Man of Steel's secret weapon while he trains her to use her powers.

Superman finally decides to reveal her to the world but tragedy strikes and she temporarily loses her powers due to the plots of a villainess from the bottled city of Kandor. During this period she is adopted by Fred and Edna Danvers. When she recovers her powers, she reveals her true identity to her adoptive parents and Superman presents her to the world.

In the meantime, while still in high school, she discovers her birth parents have actually escaped destruction by entering the Survival Zone, a dimension somewhat similar to the Phantom Zone. With the help of Fred Danvers (a scientist and engineer), she frees them and they go to live in Kandor.

After finishing Midvale High, Linda goes to Stanhope University on a scholarship, and after graduation works for a time at a TV station in San Francisco. She briefly returns to college to study acting, works for some time as a student advisor at a school in Santa Augusta, Florida, and works for a short time in New York as a soap opera actress. She leaves to go back to college, this time at Lake Shore University in Chicago.

During the crisis on Infinite Earths, Superman and Supergirl are sent with other heroes on a mission to the anti-matter iniverse. There she destroys the Anti-Monitor's machines, but is herself killed, sacrificing her life to save several Earths.