The Golden Age:
Start: c. Mid to late 1930s
Precipitating event: Creation of Superman
One Sentence Summery: Simple stories where good triumphs over evil, sometimes patriotic to the point of Jingoism.
Story Elements: During the golden age, most of the stuff was pure power fantasy. Most of the time superheroes fought normal goons that were gangsters, or occasionally an evil scientist. Good guys were always right in whatever they did, and bad guys were almost never redeemable. Also, there was very little 'conflict.' Once the hero had figured out the mystery or overcame the particular hurdle of that issue, they usually walked though the thugs and villains like tissue paper. Superheros may have fought the occasional space monster but it that was about the limit of the super-powered beings they went up against.
This was the time when many heroes (including Batman) used guns to kill people, and it was portrayed as 100% okay to do this as long as they were faceless goons. Might made right. In fact, there is a superman story where the man of steel breaks into the governor’s office, into his (basically) panic room, and intimidates him into pardoning an innocent man on death row. Lots of misogyny and racism, which was more a sign of the times than an indication of what was going on in the comic book industry as a whole.
The Industry: The reason it was called the golden age was that people were reading these comics in untold numbers that have never been seen since. It wasn't uncommon for books to sell in the tens or even hundreds of thousands of copies. There were very few crossovers and even multi-issue stories were rare. There was also almost no restrictions on the industry. Lastly, comics were seen as something both adults and kids could enjoy.
Before the US entered WWII, comics were a huge deal, though during and after WWII, they saw a massive slump in popularity. Only a few books made it through WWII (like Superman and Captain America), but they were never near the sales numbers they had before the war. For the majority of the late 40s to the 50s, superhero comics were not very popular, instead horror and detective-based comics were the most popular comics at the time.
Heroes Created at this time:Captain America, Justice Society of America (Superman, Batman, Wonder Woman, Allen Scott (1st Green Lantern), Jay Garrick (1st Flash)
Example SotM characters with a 'feel' of this era: America's Greatest Legacy, G.I. Bunker, Ra
The Silver Age
Start: c. Mid to late 50's
One Sentence Summery: Restricted storytelling with often silly stories, but we start to see hints of more depth.
Precipitating event: Creation of Barry Allen (2nd Flash)/Introduction of the Comics Code Authority
Story Elements: The CCA heavily restricted what comics could publish, making their stories more juvenile and less enticing to adults, a stigma the industry still haven't gotten over. Lots of very silly stories, (Superman even shoots Lois with a Fat ray at one point, and then mocks her for it!) However, the creation of the CCA did solidify morals in many superheroes, as they were now no longer permitted to kill. This is when Batman got his famous 'no guns' policy.
During this time we start to see the emergence of super-powered threats to superheroes (supervillains), and times when the heroes don't always win or can make mistakes. Spider-Man was particularly groundbreaking in this event, though he was still very good and moral. We start to see more challenges to superheroes during this time, and problems that heroes can't simply 'punch' their way out of.
It is important to note that this time frame encompasses all of the 60s, so there's also a great deal of psychedelic stuff here too. Drugs were never mentioned, of course, but we often see alien, bizarre worlds or dimensions that are so far removed from our own that they are unrecognizable. Doctor Strange was particularly known for this, but many other heroes also got in on the action.
The Industry: In 1954 Charles Murphy, an outraged psychologist petitioned for the creation of the Comics Code Authority which was essentially a self-policing entity for comic books. Comics would promise to adhere to certain rules and if they did so, they'd get a stamp of approval. Newstands and most major outlets would not sell comics that did not have this stamp of approval. The CCA was very restrictive, necessitating that most of the types of stories from the golden age be changed to things that were more juvenile 'silly,' and 'fanciful.
These restrictions were quite difficult for writers to get around, and limited many story ideas. Some of the restrictions were: heroes were not allowed to kill people, heroes had to dress in 'reasonable' clothing (WTF?) and alcohol and illegal drugs couldn't be portrayed in comics at all (even in a negative light.) Many themes or story elements were off-limits too, such as sympathetic villains, (“Crimes shall never be presented in such a way as to create sympathy for the criminal"), corrupt cops and politicians (“Policemen, judges, government officials, and respected institutions shall never be presented in such a way as to create disrespect for established authority.”), or the heroes being defeated (“In every instance good shall triumph over evil and the criminal punished for his misdeeds.”). In fact, the code went so far as to restrict the naming of books (“No comic magazine shall use the words "horror" or "terror" in its title.”)
Marvel/DC Heroes at this time: Too many to list! Spider-Man, Iron Man, Fantastic Four, Barry Allen (2nd flash), Hal Jordan (2nd Green Lantern) Aquaman
Example SotM characters with a 'feel' of this era: The Freedom Five, Ardent Adept, Haka
The Bronze Age
Start: c. Early 1970s
Precipitating event: Jack Kirby Leaves Marvel, Gwen Stacy is killed in Spiderman #121
One Sentence Summery: Comics start to get into politics and start to address social issues, but are mostly ham-fisted.
Story Elements: The CCA had been relaxed and changed somewhat at this point, and many new stories were now possible. Comics began to loose their 'silver age sillyness' and start to tackle real-world consequences. Many consider the death of Gwen Stacy (where Spider-Man accidentally kills Gwen Stacy by catching her with his webs too fast so that her neck snaps) the turning point. Not only does evil triumph over good in this story, but it also dealt with more mature themes like Spider-Man mourning the death of a loved one and dealing with the guilt that he killed her because of his carelessness.
This was also the time of creation for Heroes like Luke Cage, who was a superhero that primarily dealt with racial inequality. There also were a rise of female heroes that had tried to deal with gender inequality, such as a reboot to Black Widow. Additionally, both Marvel and DC decided to publish stories dealing with substance abuse (this was a risky move on their part, as those issues were not approved by the CCA). Many issues dealt with perversion of justice in the government, such that Captain America even gave up being an 'American' superhero and became 'Nomad.'
Industry: Much like the comics, the industry was striving to distance itself from the sillyness of the silver age and become socially relevant. However, most of the writers and artists at this time are still old white dudes, so their ability to write for a jive-talking black man who has faced racial inequality all his life was . . . questionable. There's clearly an attempt here to have comics take on social issues, but . . . let's just say it's not quite there yet.
Marvel/DC Heroes at this time:Luke Cage, Punisher, Wolverine, Cyborg, Vixen, Starfire
Example SotM characters with a 'feel' of this era: Unity, Mr. Fixer, Tempest, Visionary
The Iron Age (or Dark Age, sometimes).
Start: c. Mid 1980s
Precipitating event: Creation of 'event comics,' primarily 'Crisis of infinite earths.'
One Sentence Summery: Comics get darker, grittier, and more morally ambiguous, and some stray into terri-bad juvenile-ism while pretending to be 'mature.'
Story Elements: As the Bronze age became darker and more gritty, many writers lost sight of the social commentary they had started with, and bodycounts, blood, and guns started to add up. Now, there were many perfectly good comics made at this time, such as Chris Clairmont's X-men,( which started in the bronze age and went through the Iron age) which is held up as particularly good, as is DC's 'The Dark Knight Returns' and 'Watchmen.' However, many comics devolved into over-muscled guys using a ludicrous amount of guns. Super dark storylines and unnecessarily sad back-stories permeated the market.
We try not to talk about it. It should be pointed out though, that some comics did become more nuanced with their social commentary and started treating large-scale systemic social problems like something that could not be solved in a single comic book issue.
Industry: Honestly, there's an entire essay here we could talk about what happened in the industry during the Iron age. Rob Leifeld's unique style of artwork became very popular at this time (giant, overly muscled men and wafer-thin female sex-objects were the norm), and many aped his style. Additionally, there was a massive speculator boom in the 90s where the industry kept on printing new #1 issues of comics, trying to trick readers into believing they would be valuable one day. When the bubble burst, the comics industry crashed and Marvel had to actually declare bankruptcy (they got better.)
It should be obvious that the CCA changed again during this time, and also that some comic companies (namely Image Comics) didn't bother trying to make content that conformed to the CCA at all. They got away with this because of the rise in popularity of the 'direct market' (comic book stores.)
Marvel/DC Heroes at this time:Deadpool, Cable, Azrael, John Constantine
Example SotM characters with a 'feel' of this era: All the X-Treme! Prime Wardens, Normal Fanatic, Expatriette, K.N.Y.F.E.
Modern Age:
The Modern Age (Sometimes, the Electrum Age)
Start: c. 2000
Precipitating event: 'Popping' of the speculator bubble, rise of popularity of superhero movies.
One Sentence Summery: Comics are getting better all the time; inclusion and representation are up, you can get any style of story you want, but there are still some stumbling blocks.
Story Elements: The best definition of the Modern age of comics is that there is no definition. A person can find just about any type of story they want, from post-modern deconstructions of superheroes to silver age sillyness, to a more updated and sophisticated take on bronze-age comics tackling social issues. There are even some iron-age-style comics still being published. There are a few trends however, such as questioning what truly makes a hero or villain and the reformation of some villains (Superior Spider-Man). There are also several hero vs. hero stories (Marvel's Civil War I and II.) There's also an emphasis on diversity and more representation.
Industry: The industry has basically decided to run comics like a giant commercial, constantly using their many different franchises to see what works and what doesn't, and adjusting. If a movie is popular, then they incorporate elements from the movie into the comic. There is also a large emphasis on cross-overs and collected trades (collections of a storyline into a single magazine-like book.) For a while, there were large amounts of 'event comics' (Massive cross-over storylines with ramifications for an entire comic book universe, with an emphasis on buying multiple different titles in order to be caught up), but fortunately, those seem to have died down recently as readers got fatigued by them pretty quickly.
It should be pointed out that no major comic book companies follow the CCA anymore, and no one really cares about it, making it defunct at this point.
Marvel/DC Heroes at this time:Ms. Marvel (Kamala Khan), Spider-Gwen, Superior Spider-Man, Blue Beetle (Jaime Reyes), Miss Martian,
Example SotM characters with a 'feel' of this era: America's Newest Legacy, Akash'Threya, Harpy