Jefferson "Jax" Jackson born September 12,  is a mechanic and a former member of the Legends. After the death of Ronnie Raymondhe took his place as one half of the transmuted and coned meta-human called Firestorm alongside Martin Stein.
Jax was then recruited by Rip Hunter on a mission to take down Vandal Savage ; although Jax was initially unwilling to the team, Stein, who was desperate to become a time traveler and knew that he couldn't be separated from Jax for long without his powers becoming unstable, drugged him and forced him to come along. Despite ing the team against his will, Jax later grew to like being part of the team, and he began to act as the mechanic of the Waverider as well as a member and the second-in-command of the Legendsa group of individuals dedicated to protecting the timeline from time criminals.
Five years after leaving the Legends, Jax is happily married and has a daughter, Martina Jacksonnamed after Martin. He briefly re-allied with the Legends in order to stop Mallus. Jefferson was born in September 12,  to James Jackson and an unnamed woman. Two weeks after his birth, Jefferson's father was killed in an IED explosion while serving in Somalia, hurting both him and his mother. He also watched many horror movies with his mother. As a senior in high schoolJefferson was a promising football quarterback and a 4.
On December 11,Jax led his school to a victory at the game while scouts from colleges watched from the stands. These scouts were instantly impressed by his performance on the field, and his coach told him that he was talented enough to go to any school he wished. Despite that, Jefferson wasn't very popular and frequently got into fights in school.
Shortly afterward, the S. Labs particle accelerator exploded, creating Jackson of legends dating huge wave of dark matter that spread over the city.
Upon seeing the wave of energy approach, the attendants of the game ran for their lives, causing a stampede that held up one of Jax's injured teammates who relied on crutches to get around. Jax aided his teammate to safety inside of the high school, but before he could close the doors, he was struck by the dark matter at such a high speed that he was thrown backward into a wall, knocking him unconscious and slamming him into the floor.
Jax woke up in the hospital and quickly learned he could never play football again because of a permanent injury to his knee caused by the explosion. Because his family couldn't afford college and his only hope of attending college was on a football scholarship, he was ultimately forced to find a full-time job as a mechanic to support himself.
Barry and Stein had sought him out because the dark matter wave from the particle accelerator explosion changed his body's molecular structure in a way that made him one of two perfect matches to Stein, who, due to the death of his literal other half, Ronnie Raymondwas dying as a result of his powers becoming unstable from a lack of merging and needed to find a new partner. When he went to S. Labs to learn more about it and met Barry Allen's teamhe refused to merge with Professor Stein and become a superhero, a decision that caused him to be berated by Caitlin SnowRonnie's widow, for his supposed inability to take responsibility, as she did not know about his family's financial situation and had assumed that he blew off college out of laziness despite his perfect grades.
Caitlin later showed up at his auto shop and apologized for her behavior, explaining that her missing husband, Ronnie Raymondbecame a hero as Firestorm and saved Jackson of legends dating city from the singularity, inspiring Jax.
They are attacked by Dr. Henry Hewitt The other candidate to become the new Firestorm and escape to S. Labs, where Jax agrees to merge with Stein to save him resulting in the two becoming the new Firestorm. When Hewitt is wreaking havoc on Jax's old football field, he teams up with the Flash to stop Hewitt and starts to get used to his new superhuman abilities.
Afterwards, he and Professor Stein go to Pittsburgh to train on Firestorm's abilities similar to Ronnie. In JanuaryJax and Martin Stein are still in Pittsburgh, where they are up against a criminal at a chemical plant as Firestorm. While Firestorm does defeat the man, Stein is still upset that Jax doesn't listen to him, Jax tells him to stop treating him like one of his "snot-nosed undergr" when they are intercepted by Rip Hunter.
Jax and the rest of Rip Hunter's recruits woke up on top of a building where Rip informed them of the impending threat of Vandal Savage's conquest of the world and a chance to him. Later, Jax and Stein discussed Rip's offer where Jax was firmly against it while Stein relished the opportunity. However, Stein drugged him and took him on Rip Hunter's mission anyway.
Jax woke up as the team is en route to St. Roch in and was angry with Stein. Jax was left behind in the Waverider when Chronos attacked. Jax merged with Stein and provided cover for the team to escape. After learning of Rip Hunter's status as a rogue Time MasterStein and Jax discussed leaving, but Jax had a change of heart because he likes being part of a team, reminding him of his days as a football star.
They tracked down Savage to Norway. However, Savage recognized that they weren't terrorists and a huge fight broke out. Firestorm fought off Savage's criminal allies, but Ray Palmer left a part of his A. Exosuit behind, altering history. Jax accompanied Stein and Sara as they meet with Stein's younger self from in order to track down the lost part. They stole young Stein's alpha-particle tracker and used it to take Ray's tech back from Savage's minions, but young Stein tracked them back to the Waverider.
After the younger and elder Steins got into an argument, Jax consoled the elder about how arrogant both himself and his younger self are, but also how selfless and intelligent he has become. After the younger Stein was escorted off the ship, the team was contacted by Snartwho had been captured by Savage.
Firestorm took down Savage and the team escaped. However, Savage managed to get the upper hand and killed Carter and wounded Kendra forcing the team to retreat back to the Waverider. Afterwards, Jax and the rest of the team reaffirmed their commitment to defeating Savage in memory of Carter. While stuck in Leipzig inJax was tasked with fixing the jumpship which was damaged during Chronos's attack.
Leonard and Mick were getting bored on the Waverider so they convince Jax to fly them to the Central City Museum to steal the Maximillian Emerald to give it to Leonard's father. After Rip and Sara were captured trying to rescue Carter's body, Jax flies the jumpship to rendezvous with the team at the Grayhill building.
Later, Jax was present at the funeral they put on for Carter and Aldus.
The team's next mission took them to to break into the Pentagon to steal a file on Savage's current whereabouts. As Firestorm, he Jackson of legends dating tasked with creating a diversion by cutting the power, however he accidentally tripped the alarm, but they succeed on getting the file. The file directed them to the Soviet Union. Stein and Jax get into an argument where Jax is angry that he has to take all of shots, was unwillingly brought on the mission, and was forced to leave behind his life and his widowed mother in On board the WaveriderJax felt Stein's fear as he was being held and tortured in Koshmar.
Jax and Kendra use the link between him and Stein to send him a by cutting a message on his arm, which would then appear on Stein's saying that they were coming. Frustrated with being left out of the rescue efforts, Jax and Kendra convince Rip to let them help. Kendra flies Jax into the prison and he cuts the power to the locks causing a prison riot. After Vostok began to destabilize, they retreated to the jump ship. Later he and Stein make amends and Stein expressed his gratitude to have Jax as his partner. After another attack by Chronos, the Waverider is hit and the team is stranded in After the team arrived in Star City ofthey are attacked by the Green Arrow.
They retreated to the ship where Jax diagnosed the repairs that are required to get the Waverider operational again. He wanted to have Kendra's help in repairing the engines, and started to flirt with Kendra as they make repairs. Stein was able to deduce from his psychic link that Jax has a crush on Kendra and tries to deter Ray from getting close with Kendra. Stein's effort backfired, upsetting Jax but Stein told him to have more confidence in himself. Back on the WaveriderJax overheard Kendra turning down Ray and had second thoughts about asking her out.
While in the Temporal zonethe Waverider received a distress call from the Acheron.
After Mick went to make a deal with the pirates, Stein was able to sneak aboard the Acheron and free them. Jax, Stein, and Baxter acted as a distraction while Rip activated the airlock sucking the time pirates into the vacuum of space. In the aftermath of the battle, the team decided that Mick was too much of a liability, so Snart volunteered to put him down.
The updated timeline data from the Acheron pointed to Harmony FallsOregon in as the next place to find Savage. Jax was put in charge of gathering information from the local teenagers about a series of murders.
After meeting Martin and Sara during their lunch hour in a diner, he talked to Betty Seaver but some jocks tried to intimidate him.
Betty asked him out for tomorrow night. On the date, Jax asked Betty about her ex-boyfriend Tommywho went missing.
Before she could say anything, they were harassed by guys from the diner and then a horrific creature resembling Tommy attacked them. After fleeing the scene, they were pulled over by a police officer. Jax pleaded to the cop to get Betty medical help but was kidnapped by the cop.
Jax woke up inside Savage's Hall H wing and was given a dose of an Nth metal meteorite, mutating into a Manhawk. After Savage released him from his cell, Jax attacked Martin and Leonard but was knocked out by Sara. Stein and Gideon then synthesize a gene-therapy antidote curing the Manhawk mutation.
He said goodbye to Betty and told her to someday get out of Harmony Falls. The Waverider was then attacked by Chronos again and the crew was forced to leave behind Kendra, Ray, and Sara in Due to the attack, the Waverider 's was damaged so the ship touched down in instead of They picked up Kendra and Ray in Hub City. They then went to pick up Sara who had reed the League of Assassinsbut due to temporal drift, she had become detached from her former self and captured them.