Innovation is the grease in the economic engine, the sparkle that keeps culture fresh and the key ingredient in nearly every billion-dollar fortune.To kick off our yearlong series of special reports celebrating America’s 250th birthday, we present the men and women who best embody that creative spirit. All of them are in the mold of the quintessential American innovator, Thomas Edison. That means they aren’t just inventors; they’re business leaders who bring their breakthroughs to market, transforming entir ...