These are the historic events that forever transformed the United States and the world. The tragic and shocking explosion of the Space Shuttle Challenger on launch in 1986, broadcast to a shocked audience on live television. The Branch Davidian compound siege in Waco Texas in 1993 - the deadliest single operation in the history of the ATF Bureau. The Oklahoma City bombing of 1995, perpetrated by anti-government extremists Timothy McVeigh and Terry Nichols. The 2013 Boston Marathon bombing, which tore apart a race that normally brought thousands of people together. And the September 11, 2001 terrorist attacks images forever etched into the memory of a generation, heralding a world changed forever. Survivor interviews, eyewitness accounts and expert testimony bring a compelling humanity and gravitas to the stories of the Days That Shaped America.