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." Charles Moore via Steven Kasher Gallery
Sheriff's deputies in Selma prepare to confront marchers on "Bloody Sunday." Charles Moore via Steven Kasher Gallery
Activist Amelia Boynton is helped to her feet after being knocked unconscious by a state trooper. "The quality, the depth, the sense of reality that (photographer Charlie Moore) brings to the work is unparalleled," said Steven Kasher, whose gallery is showing the Selma images of Moore and other essential witnesses of the civil rights era. Charles Moore via Steven Kasher Gallery
Singer Harry Belafonte, right, was among the activists at the Selma to Montgomery marches. Charles Moore via Steven Kasher Gallery
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. Charles Moore via Steven Kasher Gallery
Belafonte, left, and Joan Baez entertained activists with music before the march. Charles Moore via Steven Kasher Gallery
Harriet Richardson, a student activist, presses a cloth to the wounds of bloodied poet Galway Kinnell in Selma. Charles Moore via Steven Kasher Gallery
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. Charles Moore/Black Star
Demonstrators in Birmingham, Alabama, huddle in a doorway to seek shelter as authorities try to disperse them with water hoses in 1963. Charles Moore/Black Star
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." Charles Moore/Black Star
The Rev. Martin Luther King Jr. is arrested for loitering outside a courtroom where his friend Ralph Abernathy was appearing for a trial in 1958.
King and his wife, Coretta, embrace in Montgomery, Alabama, in 1958. Charles Moore via Steven Kasher Gallery
In 1958, King addresses a meeting of the Montgomery Improvement Association, which was founded in 1955 to organize a bus boycott. Charles Moore via Steven Kasher Gallery