to get a little more specific:
The history of the comic book in the United States is split into several ''ages'' or historical eras: The Platinum Age, The Golden Age, The Silver Age, The Bronze Age, and The Modern Age. The exact boundaries of these eras, the terms for which originated in fandom press, is a debatable point among comic book historians. The Golden Age is generally thought as lasting from 1938's introduction of Superman until the early 1950s, during which comic books enjoyed a surge of popularity, the archetype of the superhero was invented and defined, and many of comic books' most popular superheroes debuted. The Platinum Age refers to any material produced prior to this. While comics as an artform could arguably extend as far back as sequential cave paintings from thousands of years ago, comic ''books'' are dependent on printing, and the starting point for them in book form is generally considered to be the tabloid-sized ''The Funnies'' begun in 1929, or the more traditional sized ''Funnies on Parade'' from 1933. Both of these were simply reprints of newspaper strips.
The Silver Age of Comic Books is generally considered to date from the first successful revival of the dormant superhero form — the debut of the Barry Allen Flash in ''[Showcase'' #4 (Sept.-Oct. 1956) — and last through the early 1970s, during which time Marvel Comics revolutionized the medium with such naturalistic superheroes as the Fantastic Fou] and Spider-Man. The beginings of the Bronze and Modern ages are far more disputable. Indeed, some suggest that we are still in the Bronze Age. Starting points that have been suggested for the Bronze Age of comics are Conan #1 (Oct. 1970), Green Lantern/Green Arrow #76 (Apr. 1970) or Amazing Spider-Man #96 (May 1971) (the non-Comics Code issue). The start of the Modern Age (occassionally refered to as the Copper Age) has even more potential starting points, but is most likely the publication of Alan Moore's Watchmen in 1986.
Comics published after World War II in 1945 are sometimes refered to being from the Atomic Age (refering to the dropping of the atomic bomb), and books published after Nov. 1961 are sometimes refered to as being from the Marvel Age (refering to the advent of Marvel Comics). However, these eras are refered to far less frequently than the traditional metalic eras