WASHINGTON » In 1850, the elderly master of a South Carolina estate took pen in hand and painstakingly divided up his possessions. Among the spinning wheels, scythes, tablecloths and cattle that he bequeathed to his far-flung heirs was a 6-year-old slave girl valued soon afterward at $475.

In his will, she is described simply as the “;negro girl Melvinia.”; After his death, she was torn away from the people and places she knew and shipped to Georgia. While she was still a teenager, a white man would father her first-born son under circumstances lost in the passage of time.

In the annals of American slavery, this painful story would be utterly unremarkable, save for one reason: This union, consummated some two years before the Civil War, marked the origins of a family line that would extend from rural Georgia, to Birmingham, Ala., to Chicago and, finally, to the White House.

Melvinia Shields, the enslaved and illiterate young girl, and the unknown white man who impregnated her are the great-great-great-grandparents of Michelle Obama, the first lady.

Viewed by many as a powerful symbol of black advancement, Obama grew up with only a vague sense of her ancestry, aides and relatives said. During the presidential campaign, the family learned about one paternal great-great-grandfather, a former slave from South Carolina, but the rest of Obama's roots remained a mystery.

The newly discovered story of Obama's maternal ancestors — the slave mother, white father and their biracial son, Dolphus T. Shields — for the first time fully connects the first African-American first lady to the history of slavery, tracing their five-generation journey from bondage to a front-row seat to the presidency. The findings — uncovered by Megan Smolenyak, a genealogist, and The New York Times — substantiate what Obama has called longstanding family rumors about a white forbear.

While President Barack Obama's biracial background has drawn considerable attention, his wife's pedigree, which includes American Indian strands, highlights the complicated history of racial intermingling, sometimes born of violence or coercion, that lingers in the bloodlines of many African-Americans. Obama and her family declined to comment for this article, aides said, in part because of the personal nature of the subject.

“;She is representative of how we have evolved and who we are,”; said Edward Ball, a historian who discovered that he had black relatives — the descendants of his white slave-owning ancestors — when he researched his memoir, “;Slaves in the Family.”;

“;We are not separate tribes of Latinos and whites and blacks in America,”; Ball said. “;We've all mingled, and we have done so for generations.”;

The outlines of Obama's family history unfolded from 19th century probate records, yellowing marriage licenses, fading photographs and the recollections of elderly women who remember the family. Of the dozens of relatives she identified, Smolenyak said, it was the slave girl who seemed to call out most clearly.

“;Out of all Michelle's roots, it's Melvinia who is screaming to be found,”; she said.

When her owner, David Patterson, died in 1852, Melvinia soon found herself on a 200-acre farm with new masters, Patterson's daughter and son-in law, Christianne and Henry Shields. It was a strange and unfamiliar world.

In South Carolina, she had lived on an estate with 21 slaves. In Georgia, she was one of only three slaves on property that is now part of a neat subdivision in the town of Rex, near Atlanta.

Whether Melvinia labored in the house or in the fields, there was no shortage of work: wheat, corn, sweet potatoes and cotton to plant and harvest, and three horses, five cows, 17 pigs and 20 sheep to care for, according to an 1860 agricultural survey.

It is difficult to say who might have impregnated Melvinia, who gave birth to Dolphus around 1859, when she was perhaps as young as 15. At the time, Henry Shields was in his late 40s and had four sons ages 19 to 24, but other men may have spent time on the farm as well.

“;No one should be surprised anymore to hear about the number of rapes and the amount of sexual exploitation that took place under slavery; it was an everyday experience, “; said Jason A. Gillmer, a law professor at Texas Wesleyan University, who has researched liaisons between slave owners and slaves. “;But we do find that some of these relationships can be very complex.”;

In 1870, three of Melvinia's four children, including Dolphus, were listed on the census as mulatto. One was born four years after emancipation, a suggestion that the liaison that produced those children endured after slavery. She gave her children the Shields name, which may have hinted at their paternity or simply been the custom of former slaves taking their master's surnames.

Even after she was freed, Melvinia stayed put, working as a farm laborer on land adjacent to that of Charles Shields, one of Henry's sons.

But sometime in her 30s or 40s, census records show, Melvinia broke away and managed to reunite with former slaves from her childhood on the Patterson estate: Mariah and Bolus Easley, who settled with Melvinia in Bartow Country, near the Alabama border. Dolphus married one of the Easleys' daughters, Alice, who is Michelle Obama's great-great-grandmother.

A community “;that had been ripped apart was somehow pulling itself back together,”; Smolenyak said of the group in Bartow County.

Melvinia appears to have lived with the unresolved legacy of her childhood in slavery. Her 1938 death certificate, signed by a relative, says “;don't know”; in the space for the names of her parents, suggesting that Melvinia may never have known herself.

Sometime before 1888, Dolphus and Alice Shields continued the migration, heading to Birmingham, a boomtown with a rumbling railroad, iron and steel mines and factories that attracted former slaves and their children from across the South.

Dolphus Shields was in his 30s and very light skinned — some say he looked like a white man — a church-going carpenter who could read, write and advance in an industrializing town. By 1900, he owned his own home, census records show. By 1911, he had opened his own carpentry and tool sharpening business.

A co-founder of Trinity Baptist Church, which later became active in the civil rights movement, he supervised Sunday schools at Trinity and First Ebenezer Baptist Church, which still exist today, and Regular Missionary Baptist Church.

“;He was the dean of the deacons in Birmingham,”; said Helen Heath, 88, who attended church with him. “;He was a serious man. He was about business.”;

He carried his family into the working-class, moving into a segregated neighborhood of striving black homeowners and renters. In his home, there was no smoking, no cursing, no gum chewing, no lipstick or trousers for ladies and absolutely no blues on the radio, which was reserved for hymns, remembered Bobbie Holt, 73, who was raised by Shields and his fourth wife, Lucy. She said the family went to church “;every night of the week, it seemed like.”;

He carried peppermints for neighborhood children, Holt said, and told funny stories about his escapades as a boy. But his family struggled.

His first wife, Alice Easley Shields, moved around after they split up, working as a seamstress and a maid, and two of their sons stumbled.

Robert Lee Shields, Obama's great-grandfather, married Annie Lawson in 1906 and worked as a laborer and a railroad porter, but disappeared from the public record sometime around his 32nd birthday.

Willie Arthur Shields, an inventor whose patents for improving dry cleaning operations sit in the Birmingham library, ended up working as a maintenance man, Holt said.

As for his ancestry, Dolphus Shields didn't talk about it.

“;We got to the place where we didn't want anybody to know we knew slaves; people didn't want to talk about that,”; said Heath, who said she assumed he had white relatives because his skin color and hair texture “;told you he had to be near white.”;

At a time when blacks despaired at the intransigence and violence of whites who barred them from voting, from most city jobs, from whites-only restaurants and from owning property in white neighborhoods, Dolphus Shields served as a rare link between the deeply divided communities.

His carpentry shop stood in the white section of town, and he mixed easily and often with whites. “;They would come to his shop and sit and talk,”; Holt said.

Dolphus Shields believed race relations would improve. “;It's going to come together one day,”; he often said, Holt recalled.

By the time he died in 1950 at age 91, change was on the way.

On June 9, 1950, the day that his obituary appeared on the front page of The Birmingham World, the black newspaper also ran a banner headline that read, “;U.S. Court Bans Segregation in Diners and Higher Education.”; The Supreme Court had outlawed separate but equal accommodations on railway cars and in universities in Texas and Oklahoma.

Up North, his grandson, a painter named Purnell Shields, Obama's grandfather, was positioning his family to seize the widening opportunities in Chicago.

But as his descendants moved forward, they lost touch with the past. Today, Dolphus Shields lays in a neglected black cemetery, where patches of grass grow knee-high and many tombstones have toppled.

Holt, a retired nursing assistant, said he came to her in a dream last month. She dug up his photograph, never guessing that she would soon learn that Dolphus Shields was a great-great grandfather of the first lady.

“;Oh my God,”; said Holt, gasping at the news. “;I always looked up to him, but I would never have imagined something like this. Praise God, we've come a long way.”;