Many thought the election of our first African American president put an end to the conversation about race in this country, and that America had moved into a post-racial era of equality and opportunity. Then, on the night of February 26, 2012, a black seventeen-year-old boy walking to a friend's home carrying only his cell phone, candy, and a fruit drink, was shot and killed by a neighborhood watch coordinator. And in July 2013, the trial...