Overview
The team's character and tensions are best embodied in three members: Captain America, who represents sheer heroism and nobility; Iron Man, a technological genius who represents humanity's creativity but also its frailties; and Thor, the god of myth who possesses tremendous power but can also be stubbornly single-minded, and best represents the team's struggle to serve and protect, not rule, humanity.
They have featured dozens of heroes since their inception, and stories often consider the question of what it means to be human, inhuman, or superhuman.
The 1960s
The Avengers were created as a team by Stan Lee and Jack Kirby as a group of five of Marvel's popular heroes at the time: Iron Man, The Incredible Hulk, Thor, Ant Man, and The Wasp. The apparent model for the series was the Justice League of America, a series published by rival DC Comics that featured an assortment of DC's super-powered characters. The Hulk, a volatile personality who wore clown makeup in the first issue, soon left, opening the door for the return of Captain America in The Avengers #4 (March 1964). Captain America was a 1940s patriotic hero who had been absent from comics for a decade. The comic explained his absence by stating that he'd been in suspended animation since near the end of World War II. Captain America's obsession with his dead partner Bucky Barnes provided some melodrama and a unifying theme for the series. Captain America, a trained acrobat, was considerably less powerful than the other characters, and letters to the editors commented on this fact.
The Avengers' next watershed moment was when all of the remaining founders left the team in issue #16 (May 1965), replaced by three former criminals: The Scarlet Witch, Quicksilver, and Hawkeye (the first two having been mutant foes of the X-Men). These three were less powerful than the departing members. Led by Captain America, this ushered in the long tradition of the Avengers changing line-ups periodically as members joined and departed.
Kirby was replaced as artist by Don Heck, and eventually Lee was replaced by his protege, Roy Thomas, who would become the writer probably most associated with the comic. Heroes who joined the group during this period included the Greek demigod Hercules, The Black Knight, and The Black Widow.
Thomas' biggest contribution to Avengers lore was the creation of the android hero the Vision in #57 (October 1968), who was loosely based on another 1940s hero of the same name and who turned out to be the body of the original Human Torch with the mind patterns of the villain Wonder Man. The Vision was a tragic hero due to the extent to which he stood apart from his human (or nearly-human) companions, his assimilation into human society was akin to that of Mr. Spock from Star Trek (of whom he was a contemporary).
Thomas also established that The Avengers are headquartered in a New York City building named Avengers Mansion. Their butler, Jarvis, is sometimes featured in stories which contrast the normal human experience to that of the superheroes.
John Buscema was the primary artist on the book during Thomas' 1960s run. The other highlight came in #60 (January 1969) when Ant Man (who by then had gone through identities as Giant-Man, Goliath and finally Yellowjacket) married The Wasp.
The 1970s
Thomas continued to write the book into the early 1970s. In #85 (February 1970) he introduced the Squadron Supreme, a pastiche of DC Comics' Justice League of America. Buscema left the book later that year, and the stories leading up to #100 (June 1972) included a cosmic war involving Captain Marvel, and early work by artists Neal Adams and Barry Windsor-Smith.
The next major author of the book was Steve Englehart, who introduced the character Mantis in #113 (August 1973) and wrote a number of cosmically and socially profound stories. Foremost among these was the romance and eventual marriage between The Vision and The Scarlet Witch, two outsiders who found a life together.
Englehart's tenure coincided with the debut of George Pérez on the book in #141 (August 1975). A newcomer to comics, Pérez's early work was strongly reminiscent of Kirby's, and he would go on to become one of the most popular comic book artists of the next 15 years.
After Englehart's departure, Jim Shooter took over the writing chores. He wrote a lengthy and cosmic story about a villain from the future who came to the 20th century, acquired the ultimate godlike power, and decided to become a new messiah. The story\'s strength was the tension between the lengths to which the messiah would go to achieve his goals, vs. the good he could do with his powers and the question of whether the Avengers had the right to oppose him. The story culminated in #177 (November 1978).
David Michelinie and John Byrne also contributed stories and art to the book in the 70s. New members added during this time include The Beast, a reformed Wonder Man, Captain America's former partner The Falcon, and Ms. Marvel.
The 1980s
Shooter returned with #211 (September 1981) to write a number of stories culminating in the emotional breakdown of Yellowjacket, his expulsion from the Avengers and sentencing to jail, and eventual redemption.
Many of these plot threads were carried on by the next writer, Roger Stern, who established a parallel team called The West Coast Avengers (who had their own series for about 10 years). Stern wrote the book for quite a few years, primarily illustrated by Al Milgrom, Joe Sinnott, John Buscema, and Tom Palmer.
New Avengers during the 1980s included She-Hulk, Tigra, and Hawkeye's wife Mockingbird.
The 1990s
The 1990s were a turbulent time for the Avengers, as Marvel Comics was aggressively trying to expand its business by greatly increasing the number of comics it published. This coincided with the speculators boom in the industry as a whole. Marvel then fell on hard times in the ensuing industry-wide slump, and filed for bankruptcy in 1997.
The first series of The Avengers ended with #402 (September 1996), and included 23 Annuals and 5 Giant-Size issues.
That year, Marvel contracted out several books to creators of Image Comics, and The Avengers was reborn briefly as a new series, starting with issue #1 (November 1996), throwing away the continuity of the first series. It was created by Rob Liefeld. This line of comics, called "Heroes Reborn", was ended after only a year.
Marvel then relaunched many of their main titles in a line of comics called "Heroes Return", and The Avengers volume 3 began with another #1 (February 1998), written by Kurt Busiek and drawn by George Pérez. Busiek, whose encyclopedic knowledge of comics did not get in the way of his ability to tell a good yarn, restored many classic members of the team and added a few new ones, notably Justice, Firestar and Triathlon. Pérez was succeeded by Alan Davis and then Keiron Dwyer, and Busiek wrapped up his run with a lengthy time travel story involving Kang the Conqueror. He also wrote a side limited series, Avengers Forever, illustrated by Carlos Pacheco, with similar themes.
The 2000s
Busiek was succeeded as writer on the main Avengers book with #57 (October 2002) by Geoff Johns.
Also of note is Marvel's launch of the "Ultimate" line. Intended to appeal to non-comics fans through a somewhat more realistic treatment of the characters, more lavish artwork, and no backstory to catch up on, the Ultimate version of The Avengers was called The Ultimates, written by Mark Millar and illustrated by Brian Hitch. Issue #1 was dated March 2002.