Alabama state troopers wear gas masks as tear gas is fired on marchers in 1965. Fifty years ago, about 600 people began a 50-mile march from Selma, Alabama, to the state capital of Montgomery so that they could protest discriminatory practices that prevented black people from voting. But as the marchers descended to the foot of the Edmund Pettus Bridge, state troopers used brutal force and tear gas to push them back. It is now known as "Bloody Sunday."
Sheriff's deputies in Selma prepare to confront marchers on "Bloody Sunday."
Singer Harry Belafonte, right, was among the activists at the Selma to Montgomery marches.
State police form a barricade as they wait for marchers on "Bloody Sunday."
Pam Clemson rushes to the aid of a fellow demonstrator who was felled by a blow to the head in Selma.
Belafonte, left, and Joan Baez entertained activists with music before the march.
Harriet Richardson, a student activist, presses a cloth to the wounds of bloodied poet Galway Kinnell in Selma.
A Ku Klux Klan "grand dragon" drives to a rally in North Carolina with a Klan robe hanging in the back seat of his car in the mid-1960s.
Demonstrators in Birmingham, Alabama, huddle in a doorway to seek shelter as authorities try to disperse them with water hoses in 1963.
A man looks calmly over his shoulder as a police dog in Birmingham rips his trouser leg in 1963. "The figure in the photo is a perfect symbol of nonviolence," Kasher said. "You know, the man is standing there, taking it, not fighting back, amid this incredible rush of hatred and violence and as another dog is charging right at Moore's -- at the viewer's -- face."
The Rev. Martin Luther King Jr. is arrested for loiterin