Just over 53 years ago, a bomb exploded at the Sixteenth Street Baptist Church in Birmingham, Alabama. The predominately African-American congregation was preparing for Sunday service. Four girls -- Addie Mae Collins, Denise McNair, Carole Robertson and Cynthia Wesley -- were killed. Many other people were hurt. The bombing served as the inspiration for Pulitzer Prize-winning poet Natasha Trethewey's poem, "We Have Seen." The former U.S. Poet Laureate is director of Emory University's creative