Rev. Willie Barrow, a 'superdelegate,' attending the opening night of the 2008 Democratic National Convention. The long-time activist, who was a mentor to President Obama, died on Thursday. Melanie Stetson Freeman/Christian Science Monitor/Getty hide caption

itoggle caption Melanie Stetson Freeman/Christian Science Monitor/Getty

Spider Martin's most well-known photograph, Two Minute Warning, shows marchers facing a line of state troopers in Selma moments before police beat the protestors on March 7, 1965. The day became known as Bloody Sunday. Spider Martin/Courtesy Tracy Martin hide caption

itoggle caption Spider Martin/Courtesy Tracy Martin

Tonya DeBerry (center) and her children, Herbert Nelson and Allison Nelson, have all been held in Ferguson and Jennings jails for unpaid traffic tickets. Joseph Shapiro/NPR hide caption

itoggle caption Joseph Shapiro/NPR

Rosa Parks, shown in Seattle in 1956, saved postcards from Martin Luther King Jr. and notes about carpooling during the Montgomery Bus Boycott. They're now being cataloged by the Library of Congress. Gil Baker/Courtesy of the Library of Congress, Rosa & Raymond Parks Institute for Self Development hide caption

itoggle caption Gil Baker/Courtesy of the Library of Congress, Rosa & Raymond Parks Institute for Self Development

Amy Barnes, of Marietta, Ga., has won a settlement after she says police abused her constitutional rights. Barnes was arrested and held in solitary confinement overnight for cursing at officers. David Goldman/AP hide caption

itoggle caption David Goldman/AP

Bryan Stevenson takes on cases to exonerate people wrongfully convicted. "One of the things that pains me is we have so tragically underestimated the trauma, the hardship we create in this country when we treat people unfairly, when we incarcerate them unfairly, when we condemn them unfairly," he says. Tracy King/iStockphoto hide caption

itoggle caption Tracy King/iStockphoto

A memorial sits at the site of Michael Brown's death in Ferguson, Mo. Any investigation into his shooting by a police officer is likely to take months. Larry W. Smith/EPA/Landov hide caption

itoggle caption Larry W. Smith/EPA/Landov