Fannie Lou Hamer, a one-time sharecropper who got swept up in the Southern civil rights movement of the 1960s and became one of its most powerful leaders and symbols, is dead of cancer at the age of 59.

She died Monday at all-black Mound Bayou Hospital, 30 miles from her home in Ruleville, Miss. The hospital primarily serves the poor, black, rural Mississippians for whom Mrs. Hamer spent most of her life fighting.

She endured countless threats, a number of beatings, gunshots into her home, jailings and other reprisals for her commitment to freedom for Southern blacks. And she became a symbol of unswerving black determination to overcome the laws and legacies of segregation.

"Ain't gonna let nobody turn me 'round," was one of the songs she used to lead at mass meetings all over the South.

It took a radical mastectomy and a year-long bout with cancer and other illnesses to leave her uncharacteristically drained and discouraged.

"The last day I saw Mrs. Hamer was March 4. She recognized us, but she was not in good spirits," said June Johnson, a close-friend of Mrs. Hamer since they were jailed and beaten together in Winona, Miss., in 1963.

"She was sitting in a wheel chair crying she stated she was so tired, she wanted all of us to remember her and to keep up the work. She wanted us to understand that she had taken care of business. She felt her house was in place, and that everything was in order with God, because she was a very religious person."

Mrs. Hamer first came to national attention in 1964, when the Mississippi Freedom Democratic Party she had helped found challenged the all-white regular Mississippi delegation to the Democratic National Convention in Atlantic City.

Although that challenge was not sustained by the credentials committee, it did force a walkout of the all-white delegation, as well as a party declaration that in the future, delegations would be seated only if they were broadly representative of a state's population.

Some Freedom Democratic Party delegates were seated in 1968, and in 1972, the black-led Freedom Democrats won all the seats, displacing the regular party.

Long before she came to national attention, though, Mrs. Hamer was well known among the small cadre of primarily young black Southerners and white Northerners who staged the sit-ins and freedom rides that began the breakdown of legal segregation in the south.

Born the granddaughter of a slave, the youngest of 20 children, she was sharecropping cotton on a plantation in Sunflower County when the just organized Student Nonviolent Coordinating Committee (SNCC) began working in Mississippi in 1961.

Aaron Henry, her long-time friend and co-civil rights organizer who later became state chairman of the Mississippi Democratic Party, used to talk of how John Lewis and Robert Moses discovered her talents around the time they were sent to Parehman State Prison for their organizing activities.

"She was a strong voice of natural leadership, she was very optimistic, and she was willing to sacrifice herself in order to register and vote in Sunflower County," said Archie Allen of the Voters Registration Project in Atlanta.

The young organizers who continued to pour into Mississippi and other Southern states in 1962, 1963 and 1964, and the local blacks as well, found in her a source of great spiritual strength and organizing strategy, according to many who worked with her.

The reasons may be summed up by one of the many bits of brutality that threaded through her life.

On June 9, 1963, she and June Johnson were returning to Mississippi by bus from a Southern Christian Leadership Conference workshop in South Carolina.

"As Johnson tells the story:

"When we got to Columbus (Miss.) we decided to go into the bus station and get something to eat. We were in line waiting to get on the bus and the bus driver pushed us all to the back and let all the white people on before us."

She and Mrs. Hamer discussed the incident, and decided to make an issue of it by going into the "whites only" dining room when they got to Winona, Johnson said.

"We noticed this bus driver made a stop at every small town he went through and he made phone calls, but we didn't know who he was talking to . . . When we got off at Winona, every highway patrolman and state trooper from everywhere was waiting . . ."

Despite the danger, they went on into the white only section, she said. "The cops followed us in, punched us, and told us to 'get out, niggers don't ceat on this side over here.'"

The police accused them of not knowing "how to say yes ma'am and no sir to white folks," Johnson said. They slapped, punched and kicked the two women, then took them to nearby Montgomery County jai!

At night, she said, they took Mrs. Hamer from her cell and began beating her. "We could hear her screamin' and hollering', just calling God for help . . . On the way back she fell out at our cell, just lay there cryin'. All night we could hear her crying'. She said later they had two inmates sit on her and beat her on the leg whe was crippled in."

For the rest of her life she lived with the effects of that beating, which made her carry one side of her body a little different from the other, Johnson said.

"I've never seen somebody who had been as persecuted and harassed as much as she had been and she just refused to be intimidated," said M. Carl Homan, president of the Urban Coalition.

In a 1976 interview Mrs. Hamer commented:

"The same white folks who used to drive by in pickup trucks with guns hanging up in the back giving us hate stares now call me Mrs. Hamer. They respect people who respect themselves. If we hadn't got people registered to vote, I don't think we would have had that kind of change here . . . But we've still got a long way to go."

Mrs. Hamer was brought to the Delta from the Mississippi hill country at the age of 2. Her parents and most of her 14 brothers and five sisters worked in the fields, and died as poor as they had been born, in shacks similar to those they were born in.

She talked once with pride of how she could pick 300 to 400 pounds of cotton a day, for which she was paid $1 a hundred pounds.

She might have stayed in the poverty cycle had she not been politicized by a 1961 operation. She went in the hospital to have a small uterine tumor removed. When she woke up, she found out she'd been sterilized. Doctors had given her a hysterectomy.

The anger that lingered after that incident prompted her to try to register to vote in 1962. She didn't pass the literacy test, but the attempt got her thrown off the plantation where she had lived for 19 years.

By that time she had become a field worker with the young organizers of SNCC. She started to give lectures at Northern colleges on conditions in the South, as well as speak at mass meetings in the South on the importance of trying to register to vote. And she emerged as a movement strategist.

In 1963 she helped set up a network of precinct and political organizations throughout black areas of Mississippi, the forerunner of the Freedom Democratic Party.

After the 1964 challenge at Atlantic City, she began making regular forays into the North to speak, organize and raise funds. But most of her work remained in Mississippi.

"You don't run away from problems, you just face them," she once said.

She ran against Rep. Jamie L. Whitten (D-Miss.) in the 1964 primary election and lost. In that year, of 422,256 blacks eligible to vote in Mississippi, only 28,000 were registered.

She was elected in 1971 to the steering committee of the National Women's Political Caucus, which was then a new organization. And as time went by, and more and more civil rights leaders moved away from organizing, she continued to push for change in Rulesville.

Mrs. Hamer married Perry (Pap) Hamer, who had plowed the cotton fields that she planted, in 1945. They adopted two daughters, one of whom died in 1968.

She entered a hospital in Memphis a year ago to have a cancerous breast removed. The last demonstration she participated in was one demanding reform of the Medicaid system in Jackson last December.

Mrs. Hamer had no regular income. She lived on lecture fees, contributions from friends and amirers, and, for a while, an organization called "The Friends of Fannie Lou Hamer" in Madison, Wis.

In a May, 1976, letter to a friend, she wrote, "My medicine bill is very high, but somehow . . ."

The sentence, the friend said, was never finished.