The Golden Age (1938-1956)
Superman's earliest years were a time of experimentation and development. His first appearance, in 1938's ACTION COMICS #1, was just the beginning of his evolution. Because the earliest issues of ACTION COMICS actually pre-dated the rest of the DC Universe, the concept of continuity was fluid at best. Though Superman's popularity prompted a tidal wave of new Superman stories across multiple mediums, from live-action movie serials to newspaper strips, most contributed new elements to Superman's burgeoning mythology. His powers came in piecemeal through animated shorts and radio plays which granted him abilities like flight and super-speed.
In his earliest stories, Clark was not found on the Kent farm, but by the Kents on the side of the road. They originally took him to the local orphanage before returning to adopt him properly, rather than raising him as their own from the start. In this era, Clark's move from Smallville to Metropolis was prompted by the death of his adoptive parents—a moment that inspired him to use his abilities for the good of humanity. He began working at the Daily Star as a reporter, which allowed him to chronicle his own exploits.
The earliest days of ACTION COMICS also pre-dated the DC Super-Villains as we know them today. Typically, Clark spent his early stories fighting against problems related to social unrest and World War II. It was two years after his debut before he encountered his eventual archnemesis, the mad scientist Lex Luthor (in 1940's ACTION COMICS #23). It would be another many decades before Luthor became the recognizable power-hungry businessman of the modern day.
Other pieces of the Superman mythos slowly slotted into place over the years. The Daily Star was renamed the Daily Planet in 1940. The concept of Kryptonite, the Man of Steel's most famous weakness, was formally introduced in The Adventures of Superman radio show in 1943 and made the jump to comics in 1949's SUPERMAN #61. With each passing year, no matter the medium, another part of the legend was born.
The Silver Age (1956-1970)
Superman's legacy continued to form and re-form throughout the Silver Age of comics, several decades after the Man of Steel's debut. By the 1960s, Superman enjoyed a more streamlined and solidified mythology in his various portrayals, including 1952's live-action Adventures of Superman television show and his very own Broadway musical, 1966's It's a Bird...It's a Plane...It's Superman.
In the comics of the 1960s, the Multiverse was properly formed for the first time, and the division between Earth-One and Earth-Two was drawn, with new characters like Barry Allen and Hal Jordan succeeding their Golden Age counterparts Jay Garrick and Alan Scott. For Superman, this split meant that the majority of Clark's Golden Age history was now considered to have happened to his Earth-Two counterpart, Kal-L, while his 1960s stories concerned Earth-One's Kal-El.
Throughout the Silver Age, "imaginary stories," or stories that were ultimately revealed to be the products of dreams or other illusions became popular and allowed for the exploration of any number of what-if scenarios. The marriage of Superman and Lois Lane was one such story, repeated several times throughout the era. Simultaneously, in stories both imaginary and "real," Clark faced off against a growing number of costumed super-villains like Brainiac, Metallo, Bizarro and the Parasite.
Another product of the Silver Age was the introduction of an expanded Superman family, including the creation of characters like Supergirl (Kal-El's long-lost cousin from Krypton.) The extended Superman family even grew to include super-powered animals like Beppo the Super Monkey, Krypto the Superdog and Streaky the Super-Cat.
The addition of new Kryptonian Super Heroes forced some modification to Clark's origin story and early years, which had originally positioned him as the Last Son of Krypton, the only survivor of his race, and the first Super Hero the world had ever seen. In this version of events, Clark made his public debut as Superboy rather than Superman, and had been active ever since.
MAN OF STEEL (1986)
Following 1985's continuity-altering CRISIS ON INFINITE EARTHS, Superman's history and first active decade were reimagined in 1986's MAN OF STEEL limited series.
In this version of his origin story, Clark was found by Jonathan and Martha Kent and immediately adopted. Clark's powers began to manifest in the midst of a high school football game. Jonathan and Martha then revealed the pod in which they'd first found Clark and impressed upon him the need to use his newfound abilities for good rather than for personal gain.
After moving to Metropolis, Clark anonymously tried to save people with his abilities, but soon found this impossible. Dreading becoming publicly known as an alien, Clark turned to his parents for advice. Martha promptly crafted a costume for him and suggested he assume an alter ego to preserve his privacy. Upon seeing him in action, Lois Lane gave him the name "Superman" in a Daily Planet article.
The seeds of Clark's rivalry with Lex Luthor were also planted in MAN OF STEEL, as Lex was reimagined as a smooth-talking billionaire and a duplicitous philanthropist. Lex offered Superman a job—an offer Superman summarily refused.
The Death of Superman/Reign of the Supermen (1992-1996)
Following many years of subterfuge, Superman revealed his secret identity to Lois Lane and proposed marriage in 1990's SUPERMAN #50. Lois accepted and the two became engaged.
Their impending nuptials were interrupted just two years later by the appearance of a rampaging monster named Doomsday who defeated the Justice League International and marched towards Metropolis. At the end of a brutal battle, Superman was victorious in taking down Doomsday, but at a terrible cost. In 1993's SUPERMAN #75, as the dust of his battle with Doomsday settled, Clark succumbed to his wounds and died in Lois' arms.
The vacuum created by Superman's death saw him succeeded by four "replacement" Supermen: Steel, the Last Son of Krypton (a.k.a. the alien Eradicator), Superboy (a.k.a. the Metropolis Kid), and the Cyborg Superman, all of whom claimed to be the "real" new Superman.
It was discovered that while the four new Supermen fought over the fate of Metropolis, Superman's body had disappeared from his grave. The Eradicator had placed Clark's body into a Kryptonian "regeneration matrix" which had allowed him to enter a death-like stasis and recover from his wounds. Clark eventually emerged, revived but severely depowered and wearing a black-and-silver approximation of his traditional costume. Superman was eventually repowered, and he stepped in to help stop Cyborg Superman, who'd been revealed as a super-villain named Hank Henshaw.
Following his resurrection, Clark finally married Lois Lane, paying off their proposal from years prior (SUPERMAN: THE WEDDING ALBUM, 1996).
Superman Red/Superman Blue (1997-1998)
After he was cut off from the yellow sun radiation that gave him power, Superman developed "energy based" powers (in 1997's SUPERMAN #122) which required a new electric-blue costume to contain and maintain. While wearing his new suit, Superman was able to physically transform himself into Clark Kent; but he was completely depowered after the shift, with all the vulnerabilities of a regular human.
Not long after, Cyborg Superman was able to catch Superman in a trap—a device he'd engineered with the help of the Super-Villain known as the Toyman—which caused Superman to split into two separate entities: a Blue Superman and a Red Superman (Superman Red/Superman Blue, 1998).
Both Supermen were autonomous and believed themselves to be the real Superman. They quickly grew apart from one another, to a point where did not want to merge back into one man. It wasn't until a confrontation with the Millennium Giants (in 1998's SUPERMAN #135) that the two joined into one regularly powered Superman once more. The electromagnetic abilities that had first necessitated the electric-blue costume were finally dissipated.
Infinite Crisis/Secret Origin (2005-2009)
In 2005, a new cosmic event again altered DC continuity. A follow-up to 1986's CRISIS ON INFINITE EARTHS, INFINITE CRISIS established that the Silver Age Earth-Two Superman, Kal-L, had been broken free of the "paradise" pocket dimension he, Superboy-Prime, Earth-Two Lois Lane and Alexander Luthor had been trapped in since the earlier Crisis.
Alexander Luthor and Superboy-Prime planned to re-create the Multiverse, despite the disastrous effects it would have. The two Supermen teamed up and stop them, but the resulting battle cost both Kal-L and Earth-Two's Lois their lives.
Immediately following the events of INFINITE CRISIS, Clark was depowered. He lived for a year as a civilian before his powers returned and he was able to suit up yet again (ONE YEAR LATER/SUPERMAN: UP, UP, AND AWAY!, 2006). Not long after the return of his powers, he and Lois briefly adopted an orphaned Kryptonian boy whom they named Chris Kent (ACTION COMICS #844). It was later revealed that Chris was actually Lor-Zod, the son of the Kryptonian tyrant General Zod.
The realignment of the Multiverse prompted yet another reexamination of Superman's early years in 2009's SUPERMAN: SECRET ORIGIN. This version of events re-established the idea that Clark Kent had, in fact, been Superboy during his adolescence, as well as a member of the Legion of Super-Heroes.
New Krypton (2008-2011)
During an encounter with Brainiac, the bottled Kryptonian city of Kandor was returned to its full size on Earth near the North Pole, where it became home to thousands of newly restored Kryptonians overnight (SUPERMAN: BRAINIAC, 2008).
The Kryptonians' sudden arrival prompted an immediate conflict between the governments of Earth and the leaders of Kandor, Zor-El and Alura, Supergirl's parents and Clark Kent's aunt and uncle. Tensions mounted as Lex Luthor worked to convince U.S. Army General Sam Lane (Lois' father) that the Kryptonians were not refugees, but in fact an invading army determined to wipe out humanity.
Things boiled over when Luthor and Lane's combined efforts resulted in Zor-El's death, sending Alura into a spiral of rage and grief. Kandor's engineers then lifted the city off of Earth's surface and into orbit. Alura renamed the civilization "New Krypton" and renounced humanity (SUPERMAN: NEW KRYPTON, 2009).
Eventually, Clark elected to leave Earth and live on New Krypton in the hope of fostering peace between the two governments. But a recently returned General Zod prompted even more political unrest, and ultimately New Krypton crumbled into war and chaos (SUPERMAN: WAR OF THE SUPERMEN, 2010).
The New 52 (2011-2016)
In 2011, the continuity of the DC universe was altered by the event known as Flashpoint. The resulting New 52 Universe's Clark and Lois were no longer married.
After the deaths of Jonathan and Martha Kent, their son Clark sold their farm and moved to Metropolis to pursue a career in journalism. His earliest version of the Superman costume was a t-shirt, jeans and a cape (ACTION COMICS #1-8, 2011).
In 2015's SUPERMAN #38, Clark manifested a new superpower: the ability to generate solar flares of energy which blast out from his body in all directions. Shortly after this new power developed, Lois Lane took to the internet and revealed that Clark Kent was, in fact, Superman (SUPERMAN #41, 2015). Simultaneously, it was revealed that Clark was losing control over his solar flare ability. The confluence of events prompted Clark to hang up his costume and begin acting as a street-level civilian hero around the country.
Meanwhile, through the events of 2015's CONVERGENCE, the pre-Flashpoint Superman and Lois Lane were reintroduced to continuity, a bit older, still married, and with a young son named Jon. The three existed in secret. That secrecy, however, came to an end when it was revealed the new Clark's unstable condition was fatal. In 2016's THE FINAL DAYS OF SUPERMAN, post-Flashpoint Superman was killed and pre-Flashpoint Superman, along with Lois and Jon, again stepped into the spotlight.
Following the death of the post-Flashpoint Superman and the events of 2016's DC UNIVERSE: REBIRTH #1 the pre-Flashpoint Clark Kent publicly became Superman once more.
Clark had to focus on raising his young half-Kryptonian son, Jon, whose powers were slowly beginning to manifest. Jon took on the role of Superboy, working alongside his father while Lois went back to work at the Daily Planet.
2017's SUPERMAN: REBORN dealt with the remaining loose threads of Clark, Lois and Jon's pre-Flashpoint status. It was revealed that Mr. Mxyzptlk, one of Superman's enemies, had been pushed out of time and memory during the chaos surrounding Flashpoint, and, after fighting his way out of a mysterious extra-dimensional prison, he looked to exact revenge by kidnapping Jon and forcing Clark and Lois to forget about their son. The end result of Mxyzptlk's plot was the inadvertent collision of both the pre- and post-Flashpoint timelines, merging all of Superman's history so that the entire DC Universe would remember not only that Clark and Lois were married, but that Jon Kent had been born.
Eventually, it was revealed that Mxyzptlk's captor, otherwise known as Mr. Oz, was actually Jor-El, Superman's father, who had been abducting various heroes and villains from across time and space while under the influence of some outside force (in 2017's THE OZ EFFECT).
After he was freed from corruption, Jor-El returned to Earth to offer Jon the chance to gain more understanding of his Kryptonian heritage by taking him on an interstellar pilgrimage. Though Clark initially protested, Jon was excited to go with his estranged grandfather and Lois begrudgingly agreed to join them as a chaperone, leaving Clark alone on Earth. Simultaneously, the truth of Krypton's destruction in the Rebirth era was called into question by the appearance of an alien named Rogol Zaar, who claimed he was responsible for the planet's fate (MAN OF STEEL, 2018).