The Internet has changed the past. Social media, Wikipedia, mobile networks, and the viral and visual nature of the Web have inundated the public sphere with historical information and misinformation, changing what we know about our history and History as a discipline. This is the first book to chronicle how and why it matters. Why does History matter at all? What role do history and the past play in our democracy? Our economy? Our understanding of ourselves? How do questions of history intersect with today's most pressing debates about technology; the role of the media; journalism; tribalism; education; identity politics; the future of government, civilization, and the planet? At the start of a new decade, in the midst of growing political division around the world, this information is critical to an engaged citizenry. As we collectively grapple with the effects of technology and its capacity to destabilize our societies, scholars, educators and the general public should be aware of how the Web and social media shape what we know about ourselves - and crucially, about our past.