John Stewart is an architect and veteran U.S. Marine from Detroit, Michigan, who was selected by the Guardians as a backup Green Lantern to then-current Green Lantern Hal Jordan, after the previous backup, Guy Gardner, was seriously injured after getting hit by a car while trying to save a civilian. Although Jordan objected to the decision after seeing that Stewart had a belligerent attitude to authority figures, the Guardians stood by their decision, and chided Jordan for his supposed bigoted outlook on the issue. Jordan explained that he just felt that even though Stewart might have the integrity for the task, he "obviously would have a chip on his shoulder bigger than the rock of Gibraltar."
Jordan's opinion was that Stewart’s first mission began badly. His assignment was to protect a racist politician, and Stewart, while averting an accident, took advantage of the situation to embarrass Jordan in the process. When an assassin shoots at the politician, Stewart does not intervene with Jordan in response to the attack, which initially makes Stewart seem suspect. However, it turns out Stewart had good reasons for this apparent dereliction of duty because he was stopping a gunman from killing a police officer in the outside parking lot at the event while Jordan was pursuing a decoy. When Jordan confronts Stewart about his actions, Stewart explains that the politician had staged the attack for political advantage. Jordan then concludes that Stewart was an excellent recruit and has proven his worth.
For some time, Stewart occasionally filled in as Green Lantern when Jordan was unavailable, including some missions of the Justice League.
After Jordan gave up being Green Lantern in the 1980s, the Guardians selected Stewart for full-time duty. Stewart filled that role for some years. During that period he worked as an architect at Ferris Aircraft Company, battled many Green Lantern villains, and fought against the Anti-Monitor's forces during the Crisis on Infinite Earths. John was trained in usage of his power ring by Katma Tui, the Green Lantern of the planet Korugar. The duo went on many adventures together and eventually fell in love. Kat and John went on to serve within the Green Lantern Corps of Earth alongside Hal Jordan, Arisia, Kilowog, Salaak, and other alien Green Lanterns, during which time they were married.
After John’s ring was rendered powerless through the schemes of Sinestro, and Katma Tui was murdered at the hands of the insane Star Sapphire, Stewart’s life began to unravel. First, he was falsely accused of killing Carol Ferris, Star Sapphire’s alter ego, and then falsely accused of theft by South Nambia (a fictional nation within the DC universe similar to Apartheid-era South Africa). Jailed and tortured in South Nambia for weeks, John freed himself with his old ring, now re-powered thanks to the efforts of Hal Jordan. In his escape, John inadvertently frees both a serial killer and a terrorist. When Jordan confronts John over his actions, the two friends come to blows until John realizes the “revolutionaries” he had been aiding intended to murder innocent civilians.
- John was one of the first dominant African-American heroes in the pages of DC Comics.