The correct answer is "to register African American voter in the South."
This 1964 voter registration drive was sponsored by several different organizations that aimed at gaining equal rights for African-American citizens. This included the Congress on Racial Equality (CORE) and the Student Nonviolent Coordinating Committee (SNCC). This movement to register African American voters in the South turned ugly, as groups like the Ku Klux Klan used violence to intimidate African American citizens in order to prevent them from registering to vote.