Taken from Time Magazine article "Steampunk: Reclaiming Tech for the Masses" by Lev Grossman, December 14, 2009 and reads as follows:

In 1822 the English Mathematician Charles Babbage had an idea for a machine that would perform mathematical calculations rapidly and infallibly. This was long before the age of electrical circuitry, so Babbage's plan called for the machine to be executed in brass and steel and powered by a hand crank. If it had been completed, his Difference Engine would have been a magnificent beast, requiring 25,000 parts and weighing about 15 tons. But he ran out of money and patience and had to abandon it unfinished.

Now imagine if Babbage hadn't abandoned it. Fork the timeline. Imagine if computing technology had developed along the lines of Babbage's vision: brass and steel instead of silicon and plastic; clockwork instead of electronics. In fact, imagine if all the great technological revolutions of the past 100 years hadn't happened. Our world would run on Victorian tech--it would be a handmade, steam-powered world, finished in leather and mahogany. It's an elegant, romantic vision. And it has a name: steampunk.

Steampunk has been around for at least 30 years, with roots going back further. An early example is K.W. Jeter's 1979 novel Morlock Night, a sequel to H.G. Wells' The Time Machine in which the Morlocks travel back in time to invade 1890s London. Steampunk--Jeter coined the name--was already an established subgenre by 1990, when William Gibson and Bruce Sterling introduced a wider audience to it in The Difference Engine, a novel set in a Victorian England running Babbage's hardware and ruled by Lord Byron, who had escaped death in Greece.

Ever since then, steampunk has been bubbling under: in role-playing games and anime, video games like Myst and Thief and comic books like Alan Moore's League of Extraordinary Gentlemen. Look at the dirigibles and clockwork mechanisms in Philip Pullman's alt-Victorian The Golden Compass. Recall the steam-driven, Kenneth Branagh--piloted arachnid colossus in Will Smith's Wild Wild West.

Instead of fading away, steampunk has gotten increasingly intense and relevant, and right now it seems to be rising to the surface. Scores of steampunk novels were published this year. There are steampunk housewares and steampunk bands and Victorian-inflected steampunk fashions. There are 27 steampunk iPhone apps available on iTunes. Magazines like Steampunk and blogs like Brass Goggles and the Heliograph track the scene. A museum in Oxford, England, is currently holding an exhibition of steampunk art. The steampunk meet-up at last summer's Comic-Con in San Diego was mobbed. In late October, Seattle hosted Steamcon, its first annual steampunk convention.

Scott Westerfeld, whose Uglies novels are huge best sellers, chose a steampunk setting for his new young-adult series. Leviathan, published in October, tells the story of two teenagers--an Austrian prince and an English girl passing as a boy--in a Europe divided between the Austro-Hungarian Clankers, who are technologists, and the British Darwinists, who are bioengineers. "Leviathan takes place as World War I begins, which is the end of the early era of technological romance," Westerfeld explains. "Those first tanks and other machines of war look almost comical to us now, but to the first soldiers to encounter them on the battlefield, they must have seemed like monsters. Steampunk was a way to reinvigorate that horror." 

You can read the steampunk movement as a response to the realities of modern consumer technology. Take the iPhone: its form gives no clue as to its function or who made it or where it came from. There are no screws. You can't hack it. It's perfect, but it might as well have been made by aliens and fallen to Earth in an asteroid.