How far have we come on the arc of justice?
In his speech at the end of the march from Selma to Montgomery in 1965, Martin Luther King Jr. famously said, ''...the arc of the moral universe is long, but it bends towards justice." As the Smithsonian's National Museum of African American History and Culture opens Sept. 24, we asked pioneering African-American figures, Mae Jemison, Eric Holder and Ernest Green, where our country stands on the arc today.