Every public tweet, ever, since Twitter’s inception in March 2006, is archived digitally at the Library of Congress. Twitter processes more than 50 million tweets every day, with the total numbering in the billions.
A few examples of important tweets in the past few years include the first-ever tweet from Twitter co-founder Jack Dorsey, President Obama’s tweet about winning the 2008 election, and tweets from a photojournalist who was arrested in Egypt and then freed because of a series of events set into motion by his use of Twitter.
The Library of Congress has been collecting materials from the web since it began harvesting congressional and presidential campaign websites in 2000. Today they hold more than 167 terabytes of web-based information, including legal blogs, websites of candidates for national office, and websites of Members of Congress.
Source: Library of Congress Blog