In the early 1960s, Mississippi was the poorest state in the nation. 86% of all non-white families lived below the national poverty line.  In addition, the state had a terrible record of black voting rights violations. In the 1950s, Mississippi was 45% black, but only 5% of voting age blacks were registered to vote.  Some counties did not have a single registered black voter. Whites insisted that blacks did not want to vote, but this was not true. Many blacks wanted to vote, but they worried, and rightfully so, that they might lose their job. In 1962, over 260 blacks in Madison County overcame this fear and waited in line to register. 50 more came the next day. Only seven got in to take the test over the two days, walking past a sticker on the registrar's office door that bore a Confederate battle flag next to the message "Support Your Citizens' Council."  Once they got in, they had to take a test designed to prevent them from becoming registered. In 1954, in response to increasing literacy among blacks, the test, which originally asked applicants to "read or interpret" a section of the state constitution, was changed to ask applicants to "read and interpret" that document.  This allowed white registrars to decide whether or not a person passed the test. Most blacks, even those with doctoral degrees, "failed." In contrast, most whites passed, no matter what their education level. In George County, one white applicant's interpretation of the section "There shall be no imprisonment for debt" was "I thank that a Neorger should have 2 years in collage before voting because he don't under stand." (sic)  He passed.
The NAACP went to Mississippi in an effort to register more blacks in the late 1950s. Amzie Moore, a local NAACP leader in Mississippi, met with SNCC worker Robert Parris Moses when Moses traveled through the state in July 1960, recruiting people for a SNCC conference. Moore encouraged Moses to bring more SNCC workers to the state, and the following summer he did, beginning a month-long voter registration campaign in the town of McComb, in conjunction with C.C. Bryant of the NAACP. SNCC organized a voter registration education program, teaching a weekly class that showed people how to register.
SNCC worker Marion Barry arrived on August 18 and started workshops to teach young blacks nonviolent protest methods. Many of the blacks, too young to vote, jumped at the opportunity to join the movement. They began holding sit-ins. Some were arrested and expelled from school. More were expelled when they held a protest march after the murder of Herbert Lee, who had helped SNCC workers, on September 25. In response to these expulsions, Moses and Chuck McDew started Nonviolent High School to teach the expelled students. They were arrested and sentenced to four months in jail for "contributing to the delinquency of minors." 
Other protests by blacks were met with violence. At sit-ins which began on May 28, 1963, participants were sprayed with paint and had pepper thrown in their eyes. Students who sang movement songs during lunch after the bombing of NAACP field director Medgar Evers' home were beaten. Evers himself was the most visible target for violence. He was a native of Mississippi and World War II veteran who was greeted by a mob of gun-wielding whites when he attempted to register after the war in his hometown of Decatur. He later said, "We fought during the war for America, Mississippi included. Now, after the Germans and Japanese hadn't killed us, it looked as though the white Mississippians would." After he was denied admission to the University of Mississippi law school, he went to work for the NAACP. By 1963, Evers was aware that, in the words of his wife Myrlie Evers,
. . . Medgar was a target because he was the leader. The whole mood of white Mississippi was that if Medgar Evers were eliminated, the problem would be solved. . . . And we came to realize, in those last few days, last few months, that our time was short; it was simply in the air. You knew that something was going to happen, and the logical person for it to happen to was Medgar.
At an NAACP rally on June 7, Medgar Evers told the crowd, "Freedom has never been free . . . I love my children and I love my wife with all my heart. And I would die, and die gladly, if that would make a better life for them."  Five days later, he was shot and killed as he returned home around midnight. Byron de la Beckwith, a member of the Citizens' Council, was arrested for Evers' murder, but he was set free after two trials ended in hung juries. He later ran for lieutenant governor.
That fall, the Council of Federated Organizations (COFO), an umbrella organization of local and national civil rights groups founded in 1962, organized the Freedom Vote. The Freedom Vote had two main goals:
- To show Mississippi whites and the nation that blacks wanted to vote and
- To give blacks, many of whom had never voted, practice in casting a ballot
The mock vote pitted the actual candidates against candidates from the interracial Freedom Party. 60 white students from Yale and Stanford Universities came to Mississippi to help spread word of the Freedom Vote. 93,000 voted on the mock election day, and the Freedom Party candidates easily won. 
After the success of the Freedom Vote, SNCC decided to send volunteers into Mississippi during the summer of 1964, a presidential election year, for a voter registration drive. It became known as Freedom Summer. Bob Moses outlined the goals of Freedom Summer to prospective volunteers at Stanford University:
- to expand black voter registration in the state
- to organize a legally constituted "Freedom Democratic Party" that would challenge the whites-only Mississippi Democratic party
- to establish "freedom schools" to teach reading and math to black children
- to open community centers where indigent blacks could obtain legal and medical assistance 
800 students gathered for a week-long orientation session at Western College for Women in Oxford, Ohio, that June. They were mostly white and young, with an average age of 21. They were also from well-to-do families, as the volunteers had to bring $500 for bail as well as money for living expenses, medical bills, and transportation home. SNCC's James Forman told them to be prepared for death. "I may be killed. You may be killed. The whole staff may go." He also told them to go quietly to jail if arrested, because "Mississippi is not the place to start conducting constitutional law classes for the policemen, many of whom don't have a fifth-grade education." 
On June 21, the day after the first 200 recruits left for Mississippi from Ohio, three workers, including one volunteer, disappeared. Michael Schwerner, Andrew Goodman, and James Chaney had been taken to jail for speeding charges but were later released. What happened next is not known. Local police were called when the men failed to perform a required check-in with Freedom Summer headquarters, but Sheriff Lawrence Rainey was convinced the men were hiding to gain publicity. The FBI did not get involved for a full day. During the search for the missing workers, the FBI uncovered the bodies of three lynched blacks who had been missing for some time. The black community noted wryly that these murders received nowhere near the same nationwide media attention as the murders of the three workers, two of whom were white.
Meanwhile, Freedom Summer went on. Only a handful of recruits left the orientation session in Ohio. The volunteers helped provide basic services to blacks in the South. "Freedom clinics" provided health care; Northern lawyers worked in legal clinics to secure basic constitutional rights; "freedom schools," though illegal, taught blacks of all ages traditional subjects as well as black history. 
One of Freedom Summer's most important projects was the establishment of the Mississippi Freedom Democratic Party (MFDP) to challenge the all-white regular Democratic party in the state. This project actually started before Freedom Summer did, when MFDP won crucial support from the California Democratic Council, a liberal subsection of the state's Democratic party, and Joseph Rauh, head of the DC Democratic Party, vice president of Americans for Democratic Action (ADA), and general counsel to the United Auto Workers. President Johnson, however, backed the regular Democratic party because he could not afford to lose their political support. 
In June, the names of four MFDP candidates were on the Democratic primary ballot as delegates to be sent to the Democratic National Convention in Atlantic City, but all four lost. Later that month, the regular Democratic party adopted a platform that explicitly rejected the national party platform in the area of civil rights. This put President Johnson in a difficult position. The national Democratic organization required all delegates to make a pledge of party loyalty, but Johnson had to allow the Mississippi Democrats to be seated because otherwise delegates from five other states would walk out. The Mississippi issue was turning what should have been a quiet, routine convention into a racial battleground.
On August 4, the bodies of the three civil rights workers were found in a dam on a farm near Philadelphia, Mississippi. They had all been shot and the one black, James Chaney, had been brutally beaten. The discovery shifted media attention back to Mississippi just 18 days before the start of the Democratic National Convention. Two days later, the MFDP held a convention and selected a 68-person delegation, which included four whites, to go to the national convention. By now, the party had the support of ADA, delegates from nine states, and 25 congressmen. The delegates wanted to be seated instead of the regular delegates at the convention. To do so, they had to persuade eleven of the more than 100 members of the Credentials Committee to vote in their favor. They decided to provide testimony detailing how difficult it was for blacks to vote in Mississippi. Fannie Lou Hamer, one of twenty children of Mississippi sharecroppers, gave an impassioned speech to the Committee:
If the Freedom Democratic Party is not seated now, I question America. Is this America? The land of the free and the home of the brave? Where we have to sleep with our telephones off the hook, because our lives be threatened daily? 
President Johnson quickly called a press conference to turn news cameras away from Atlantic City, but the evening news that night showed portions of Hamer's testimony. Her emotional statement moved people around the nation.
Senator Hubert Humphrey offered a compromise, with the blessing of the president. The white delegates would be seated if they pledged loyalty to the party platform. Two MFDP delegates, Aaron Henry and Ed King would also be seated, but as at-large delegates, not Mississippi delegates. Neither side liked the agreement, but in the end, both sides accepted. The trouble, however, was not over. When all but three of the Mississippi delegates refused to pledge allegiance to the party, the MFDP delegates borrowed passes from sympathetic delegates and took the seats vacated by the Mississippi delegates until they were thrown out. The next day, they returned. The empty seats had been removed, so the delegates just stood and sang freedom songs.
In the end, the Mississippi Freedom Democratic Party, like the Freedom Riders, did not fully accomplish its goals. The MFDP, however, was far from a failure. It showed blacks that they could have political power. It ensured that, in the words of Joe Rauh of ADA, "there will never be a lily-white [delegation] again."  It raised the important issue of voting rights, reminding America that the recently-passed Civil Rights Act, which disappointed black leaders because it did not address the right to vote, was not enough. It also helped blacks and other minorities gain more representation in the Democratic party. Freedom Summer, too, was an overall success. Clayborne Carson wrote:
When freedom school students from across the state gathered for a convention early in August, their increased confidence and political awareness were manifest in their approval of resolutions asking for enforcement of the Civil Rights Act of 1964, . . . elimination of the poll tax, and many other reforms. 
There is no denying the effect that Freedom Summer had on Mississippi's blacks. In 1964, 6.7% of Mississippi's voting-age blacks were registered to vote, 16.3% below the national average. By 1969, that number had leaped to 66.5%, 5.5% above the national average.