Courtney Whitmore is a junior member of the Justice Society of America and the JSA All-Stars. She originally operated as Star-Spangled Kid using Sylvester Pemberton's Cosmic Converter Belt, but when Jack Knight left her the Cosmic Staff, she adopted the name Stargirl. With the belt and the staff, she carries on the legacies of Star-Spangled Kid and Starman.
Courtney was the daughter of Sam Kurtis and Barbara Whitmore, born and raised in sunny California. Her parents broke up, and Barbara found a new love: Pat Dugan. They moved to Blue Valley, Nebraska. Courtney did not like the move, and she did not like her new stepdad. She did make new friends quickly, though, with Mary Kramer and Josh Hamman.
While rummaging through her stepfather's belongings, she found Sylvester Pemberton's old equipment. Realizing her stepdad used to be Stripesy, the only adult sidekick to a teen hero in history, filled her with joy, as she had a new means to get back at him and ridicule him. She donned a Star-Spangled outfit to a patriotic-themed spirit week dance to mock him, but they were attacked by Dragon King's minions. Dugan pulled out his newly built S.T.R.I.P.E. armor to stop them, and they prevented the thugs from taking over. They decided they would form a duo, Star-Spangled Kid and S.T.R.I.P.E.
The attack on the high school caught the attention of Oracle, who clued Robin in on the new legacy hero. Though they had little to go on, Young Justice traveled to Nebraska to take a look at the new hero. Their initial meeting was not smooth (as they kept thinking the S.T.R.I.P.E. armor was a robot) but in the end, they solved an alien invasion together.
Courtney did not join the Team, but she did come along on their mission to Zandia to stop Agua Sin Gaaz.
Adventures in Blue Valley
In Blue Valley, most of her adventures involved Dragon King, and his daughter, Cindy Burman. Cindy was the most popular girl in school, and as evil as her father. She adopted the name Shiv, and would become Courtney's arch nemesis.
During her adventures, she teamed up with Starman and the Shining Knight, who carried a grudge against Dragon King as he had killed his love Firebrand.
When Jack Knight retired as Starman, he knew who to give his staff to. He had previously met Courtney, and was impressed how she managed during Sins of Youth. She had wielded the Staff then, so as he left for San Francisco to raise his son Kyle, he passed the staff and the legacy of Starman to her. She added the Cosmic Staff to her arsenal. Some time later, she decided to adopt the name Stargirl, a name Mary had suggested to her when she first became a hero.
She only sporadically saw her biological father, Sam Kurtis, and when she did, it was not in a positive light. When she found him working as a low-level goon for the Royal Flush Gang, she broke with him for good. She started seeing Pat as her father, which was cemented when she learned of Kurtis's death.
Stargirl was a much appreciated junior member of the Justice Society. She learned a lot from Power Girl, and had a brief fling with Billy Batson. That the rest of the Society did not know Captain Marvel was actually a fourteen year old hampered the relationship, and led to Captain Marvel quitting the JSA. Al Rothstein and Jakeem Thunder also had an affection for her. She did have feelings for Al, and even saw a vision of them being married in the future. When he was tried for the massacre in Khandaq, she told him she would wait for him.
While other members of the Justice Society were phased from the main Earth to the new Earth-Two, Whitmore along with teammates Mister Terrific and Doctor Mid-Nite remained, revealing that they would not have been native to Earth-Two.
Stargirl survived the Crisis largely intact, and began attending college. She changed her equipment: her rod now compresses to a small cylinder, and when she activates it, her costume and belt appear while the rod grows to full size. She has started to take driving lessons from Mr. Terrific.
Less than a year after the Infinite Crisis, the JSA was disbanded when only three members remained. When the time was right, Green Lantern, Flash and Wildcat set it up again, and Stargirl was a solid choice. She became friends with Ma Hunkel's granddaughter, Maxine Hunkel, and helped her form her identity Cyclone.
When the JSA split up due to differences between the old guard and the new, Courtney decided to join the JSA All-Stars. At first she felt out of place because everyone was older than her, but Power Girl convinced her that they needed her and that she was a role model to most of the members. During this time, Albert Rothstein was missing and Johnny Sorrow claimed to be in love with her. He took her to the subtle realms disguised as Atom Smasher in order to receive a kiss from the girl. The real Atom Smasher was tied up at a castle in the realms and the JSA All-Stars came to save her. At the end, Courtney continued her work with the All-Stars. She also attempted to patch up her relationship with Albert, but they soon realized that they both had a need for space.