Fifty years ago, in response to the surprise Soviet launch of Sputnik, the U.S. military set up the Advanced Research Projects Agency. It would become the cradle of connectivity, spawning the era of Google and YouTube, of Amazon and Facebook, of the Drudge Report and the Obama campaign. Each breakthrough—network protocols, hypertext, the World Wide Web, the browser—inspired another as narrow-tied engineers, long-haired hackers, and other visionaries built the foundations for a world-changing technology. Keenan Mayo and Peter Newcomb let the people who made it happen tell the story.