Days That Shaped America

The Boston Marathon brought people together-until two suspects tried to tear it apart.

Could one of the most tragic and shocking moments in NASA's history have been prevented? Go inside the heartbreaking loss of the Space Shuttle Challenger, from those who were there.

What began as a calm spring morning in Oklahoma City erupted into the largest terrorist act America had yet seen. What drove Timothy McVeigh's brutal act, which killed 168 people?

The largest terror attack in our nation's history left images seared into our conscience that will never be forgotten. But for those caught in the middle, the memories are as strong today as they were in 2001.

Hear from those involved in the 1993 siege on the Branch Davidian compound in Waco, Texas, a 51-day standoff between the FBI and David Koresh and his followers that ended in tragedy.