Unlike others who bear the name "Green Lantern," Alan Scott's power does not come from the Guardians of the Universe, but from the Starheart, an magical entity once imprisoned by the Guardians. The Starheart found its way to Earth where, in 1939, in the shape of a lantern, it saved Alan from a train wreck. At the lantern's mental direction, Alan fashioned a ring from it that allowed him to tap the Starheart's great power. Perhaps influenced subconsciously by the Starheart's history, Alan adopted the identity of Green Lantern (the name of the great Corps administered by the Guardians).
Alan was a founding member of the Justice Society and was instrumental in many wartime battles. After the war, as a broadcast executive in the late forties, Alan Scott had a flirtatious relationship with the costumed villainess the Harlequin (who unbeknownst to Alan, was secretly his secretary, Molly Maynne). Molly even admitted that her career as a "criminal" was just a ruse to get close to Green Lantern. The Harlequin eventually turned over a new leaf, becoming an undercover agent for the FBI. She left Alan's life without confessing her true identity or her real feelings.
Alan subsequently met and quickly married a young woman named Alyx Florin. He was unaware that she was actually Rose Canton (a.k.a. The Thorn), a schizophrenic but reformed enemy of the Flash. Alyx disappeared on their wedding night, starting a fire that led Alan to believe she had died. In fact, she survived and discovered that she was pregnant with twins. The children were born in Milwaukee, Wisconsin and raised separately by adoptive families as Jennifer-Lynn Hayden and Todd Rice. Alyx was taken to the Amazons' Reformation Island.
Jennie-Lynn and Todd, who developed superhuman powers as a result of their father's connection to the mystic Starheart, did not meet until adolescence, and set out to uncover the identities of their real parents. They adopted the costumed identities of Jade and Obsidian and confronted Alan about their parentage. And truly, Alan had no clue. Also during this time, he renewed his acquaintance with Molly and discovered her past as the Harlequin; the pair finally gave in to their longtime attraction. But Rose Canton also resurfaced. Just before her death, she revealed the circumstances of Jennie and Todd's births. Alan and Molly were married, but soon separated by the JSA's banishment to Limbo. They were reunited two years later when the Justice Society returned to Earth.
Recently, the Starheart made Alan appear much younger, and he took the new name and costume, Sentinel. He encountered a mysterious new Harlequin (IV), who may have been a manifestation of the Starheart, which became malevolent. The Starheart was apparently destroyed and Alan's powers were diminished and he returned to his original uniform. Jade also lost her powers during this incident.
When the Justice Society reformed, Alan was there as always to anchor the team. One of their first major cases pitted Sentinel against his son, Obsidian, who had been seduced by dark forces. Alan was forced to beat Todd into retreat. It soon became obvious (and was confirmed by Dr. Mid-Nite) that Alan had become the living embodiment of the Starheart. Any changes to his age or powers are merely psychosomatic. Obsidian returned in alliance with Mordru and Eclipso. This time, Alan set things right and banished Todd's dark powers, perhaps for good. After this, Alan reclaimed the name Green Lantern. Todd was taken into D.E.O. custody and vowed to atone for his actions. The recent events involving his son have made Alan somewhat overbearing and overprotective of the JSA's other "children."
During the great Crisis created by Alexander Luthor and Superboy-Prime, Alan and Jade followed Donna Troy into space to investigate a cosmic rift. When Luthor was defeated, the rift began collapsing and Jennie-Lynn was caught in one of the shock waves. Alan was on Thanagar when she lost her life. He learned afterwards that as she died, she returned the power once given to her by Kyle Rayner. Thus in a way, she continues to live on within Rayner.
When the rift collapsed for good, Alan and the remaining heroes were sent reeling through space and time. He and several others reemerged a week later on Earth. Alan was among the lucky ones, having only lost an eye. Alan then somehow gained Adam's right eye and lost his left eye completely.
His missing eye was later replaced by a portion of his daughter Jade's mystic green energy. After being put into a comatose state during an attack by the Gentleman Ghost, Jade appeared to him, told him goodbye and granted him another portion of her green energy. His missing eye is currently replaced by a green glowing orb that, due to its mystical origins and connection to Jade, allows him to track astral and mystical energy forms such as ghosts.
The JSA had also become a spectre of its former self, and its members became disillusioned about the team's effectiveness. This was underscored by the advent of Lex Luthor's Everyman technology, which awarded powers to a girl who adopted Jade's codename. Alan had to restrain Obsidian from accosting the girl.
Soon Alan was approached by the spy organization Checkmate, which was reorganizing under U.N. control. They invited Alan to become their White King, which he accepted. His time with Checkmate was brief.
Scott soon found himself in a moral conflict with Checkmate's Black Knight Sasha Bordeaux over the violent nature of Checkmate, particularly after Bordeaux and her team slaughtered dozens of Kobra operatives during a raid on a facility. Bordeaux contended that the ends justified the means, while Scott adhered to the principle that heroes should not kill unless absolutely necessary; Bordeaux responded to this by suggesting that Scott should resign. Concurrent with this internal conflict, Scott and "White Queen" Amanda Waller attempted to keep the organization from being discontinued by political forces.
Another JSA member, Mr. Terrific, succeeded him in the post.
Meanwhile, Alan was urged by the Justice League to re-establish the JSA as an organization that cares for the legacy of its heroes. When his time with Checkmate came to an end, Alan resumed an active role in the JSA.