Spider-Man's Tangled Web #20, with a publishing date of January, 2003, featured the story "Behind the Mustache" which focused on his childhood and years as a teenager. According to it he was born to David and Betty Jameson. His father was an officer of the United States Army, a war veteran decorated as a hero but an abusive husband and father. As a result he grew convinced that "No one's a hero every day of the week" and "Even the real heroes can't keep it up all the time". Jonah was a Boy Scout during his childhood. In high school his interests were mainly boxing and photography. He met his later first wife Joan when they both joined their high school's photo club. The members of the club were used to being subjects of bullying by three of the school's athletes. But when they attempted to treat the club's new member Jonah in the same way, they only ended up being beaten up by him. Jonah impressed Joan and they started dating. They married as soon as they finished school.
After school Jonah seeked employment as a journalist. According to Marvels #1, he found employment in the Daily Bugle and bragged to his colleagues that he would one day run the newspaper. In 1939 he was witness to the first appearances of Jim Hammond, the android Human Torch, and Namor McKenzie, the Sub-Mariner, Prince of Atlantis, who are jointly considered Marvel's first superheroes. He was less than convinced that they were so heroic and even less pleased that their powers outshone any regular person. When the USA joined World War II in 1941, Jonah served as a war journalist in Europe. Sergeant Fury and His Howling Commandos #110 featured him as covering a mission of Sergeant Nicholas Fury, head of a team of commandos during the war (and later agent and eventually director of S.H.I.E.L.D, a fictional secret agency playing an important role in the Marvel Universe).
Following the end of the war Jonah continued his career. He and Joan had a son John Jameson. When Jonah returned from a journalistic mission covering the Korean War (June 25, 1950 - July 27, 1953) he was grieved to find that his wife had died during his absence. Focusing even further in his professional life he was eventually promoted to chief editor of the Daily Bugle and later yet managed to gain ownership over it.
In Amazing Spider-Man #162, with a publishing date of November, 1976, Jonah first introduced himself to Dr. Marla Madison, a distinguished scientist and daughter of a deceased friend of his. He asked for her help in creating a new Spider-Slayer, one of a series of robots created to slay Spider-Man, although the latter has managed to survive their attacks and destroy each one of them. Marla was interested in the challenge and joined Jonah in his efforts. Though Marla was about the same age as Jonah's son the two eventualy grew closer and ended up marrying each other in Amazing Spider-Man (volume 2) #18, published in 1984. Jonah remains a devoted, if a little over-protective, husband to his second wife.
As a publisher Jonah has a mostly deserved reputation for journalistic integrity, but he is not an easy man to like. JJJ is plagued by greedy opportunism and unyielding stubbornness that is especially linked to a pathological hatred for Spider-Man.
He has acted on this hatred by continually accusing the superhero of any wrongdoing in his publications, only to be continually obliged to print almost as many retractions after being proven wrong. Even the numerous times that Spider-Man saved his and his loved ones lives have not changed his mind, only increasing his determination to find some flaw in the hero.
In addition, his efforts to stop Spider-Man included posting rewards for his capture or secret identity, hunting him for capture with Alister Smyth's Spider Slayer robots and even commissioning super powered agents to defeat the hero. The last one proved to be his most costly blunder, especially with the enhancement of a private detective called Mac Gargan into the Scorpion, who soon lost his sanity and turned on JJJ. Furthermore, the guilt of being responsible for creating that destructive pyschopath weighed on him years and was even used for blackmail by the Hobgoblin.
For all his hostility towards Spider-Man, he has a great need for news photographs of Spider-Man, and Peter Parker soon took advantage of that by taking pictures of himself as Spider-Man and selling them to the Bugle with few questions.
To his credit, Jameson has also been a tireless crusader for civil rights, labour union rights, cleaning up corruption and has gone after organized crime despite repeated threats and attempts on his and staff's lives.