23 KEYS MOMENT FROM TWITTER HISTORY

A billion messages are sent on Twitter every 2½ days. That's three for every man, woman and child in the United States. Sure, the vast majority of tweets haven't made history. But there have been no shortage of big moments for Twitter since its debut more than seven years ago. That's part of the reason Twitter has become a digital watercooler of sorts for global conversations around live TV events such as elections, the Oscars or the Super Bowl. With news that Twitter has filed to become a publicly traded company, we took a look back at some of the key moments from its brief history. From celebrity-driven milestones to political downfalls to tweets from space, they've been as diverse as the more than 200 million people who now use the site. May we present seven years of famous, and infamous, tweets and Twitterers: March 2006 -- The first-ever tweet was posted by co-founder Jack Dorsey as part of an internal messaging system for Odeo, the podcasting company where Dorsey, Biz Stone and Evan Williams worked at the time. It said simply, "just setting up my twttr." July 2006 -- The full version of Twitter was introduced publicly on July 15, although Twitter didn't spin off into its own company until the next year. March 2007 -- Although not yet mainstream, Twitter exploded in popularity among early adopters at the South By Southwest Interactive festival in Austin, Texas. In a clever move, the company placed large screens in conference hallways that displayed live tweets about SXSW events. Buzz quickly grew, and by the end of the week, daily Twitter usage had tripled. April 2008 -- In an early example of the power of Twitter, an American graduate student used the service to alert his friends that he had been arrested at an anti-government protest in Mahalla, Egypt. After mounting pressure, authorities released him from jail the next day. January 2009 -- A US Airways plane with 155 people on board made a miraculous emergency landing on the Hudson River after striking a bird during takeoff. An eyewitness tweeted out a widely shared photo of passengers waiting on the plane's wing to be rescued, cementing Twitter's status as a real-time, news-gathering tool.