SELMA, Ala. -- Crowds gather on March 7, 2015, before a speech by President Barack Obama marking the 50th anniversary "Bloody Sunday," a civil rights march in which protesters were beaten, trampled and tear-gassed by police at the Edmund Pettus Bridge, in Selma, Ala.
Demonstrators march over the Brooklyn Bridge to mark the 50th anniversary of the landmark event of the civil rights movement in Selma, Ala., on March 7, 2015, in New York. (AP Photo/John Minchillo)
Mercedes Binns, who has been to Selma 17 times because of its civil rights history, walks on the Edmund Pettus Bridge, Sunday, March 8, 2015, in Selma, Ala. (AP Photo/Bill Frakes)
The Rev. Martin Luther King III walks with supporters before President Barack Obama gives a speech in Selma, Ala. to mark the 50th anniversary of "Bloody Sunday" on March 7, 2015. (AP Photo/Bill Frakes)
Singing "We Shall Overcome," President Barack Obama, fourth from left, walks holding hands with Amelia Boynton, who was beaten during "Bloody Sunday." (Jacquelyn Martin)
President Barack Obama exits Air Force One with daughter Malia Obama, left, and Sasha Obama, on arrival at Maxwell Air Force Base in Montgomery, Ala. (AP Photo/Jacquelyn Martin)
President Barack Obama speaks near the Edmund Pettus Bridge, Saturday, March 7, 2015, in Selma, Ala. (Bill Frakes)
The United States Secret Service drives across the Edmund Pettus bridge with President Barack Obama on March 7, 2015, in Selma, Ala. (AP Photo/Gerald Herbert)
President Barack Obama speaks by the Edmund Pettus Bridge in Selma, Ala., Saturday, March 7, 2015, for the 50th anniversary of "Bloody Sunday." (Jacquelyn Martin)
A large crowd forms near a stage where President Barack Obama will speak and then take a symbolic walk across the Edmund Pettus Bridge on March 7, 2015, in Selma, Ala. (AP Photo/Gerald Herbert)
The Rev. Al Sharpton waves to supporters before President Barack Obama and others take a symbolic walk across the Edmund Pettus Bridge on March 7, 2015, in Selma, Ala. (AP Photo/Gerald Herbert)
A large crowd forms near a stage where President Barack Obama spoke and took a symbolic walk across the Edmund Pettus Bridge on March 7, 2015, in Selma, Ala. (AP Photo/Gerald Herbert)
A large crowd forms near a stage where President Barack Obama will speak and then take a symbolic walk across the Edmund Pettus Bridge on March 7, 2015, in Selma, Ala. (AP Photo/Gerald Herbert)
The Rev. Jesse Jackson speaks with people before President Barack Obama and others take a symbolic walk across the Edmund Pettus Bridge on March 7, 2015, in Selma, Ala. (AP Photo/Bill Frakes)