“You know, we have that in our own family too.” That was the bombshell, the offhand remark that plunged historian Allyson Hobbs, AM’02, PhD’09, into a 12-year odyssey to understand racial passing in America—the triumphs and possibilities, secrets and sorrows, of African Americans who crossed the color line and lived as white. As a first-year graduate student at the University of Chicago, Hobbs happened to mention to her aunt the subject of passing, a casual curiosity sparked by the Harlem Renaissance writers she was reading in school. Her aunt responded by telling her the story of a distant cousin from the South Side of Chicago who disappeared into the white world and never returned.

That story opens Hobbs’s book, A Chosen Exile: A History of Racial Passing in American Life (Harvard University Press, 2014), a lyrical, searching, and studious account of the phenomenon from the mid-19th century to the 1950s. Hobbs’s cousin was 18 when she was sent by her mother to live in Los Angeles and pass as a white woman in the late 1930s. “And our cousin—and this was the part of the story that my aunt really underscored—was that our cousin absolutely did not want to do this,” Hobbs says. “She wanted to stay in Chicago; she didn’t want to give up all her friends and the only life she’d ever known.” But her mother was resolved. And so the matter was decided.

Ten or 15 years later, her cousin got what Hobbs calls an “inconvenient phone call.” Her father was dying. And her mother wanted her to come home right away. “And she says to her mother, ‘I can’t come home. I’m a white woman now.’” She was married to a white man; she had white children. “So she never goes back,” Hobbs says.

Many threads weave through A Chosen Exile, released last fall to glowing reviews: the meaning of identity, the elusive concept of race, ever-shifting color lines and cultural borderlands. But by far the book’s most potent thread is about loss. “The core issue of passing is not becoming what you pass for,” Hobbs writes in the prologue, “but losing what you pass away from.” Historians have tended to focus on the privileges and opportunities available to those with white identities. Hobbs reckons with the trauma, alienation, and scars—not only for those who passed, but also for those they left behind. In letters, unpublished family histories, personal papers, sociological journals, court cases, anthropological archives, literature, and film, she finds “a coherent and enduring narrative of loss.”

One story Hobbs tells is of Elsie Roxborough, a socialite who briefly dated Joe Louis and Langston Hughes, and who in 1937, after graduating from the University of Michigan, began passing as white to become a model. She never settled down, moving from California to New York, where she changed her name to Mona Manet. She committed suicide in 1949. Only her sister and aunt, both light skinned, traveled to New York to claim her body. “The arrival of these two ostensibly white women allowed Elsie to remain white, even in death,” Hobbs writes.

Hobbs also describes the upper-class Johnston family, who in the early 1900s became stalwarts of social and civic life in an all-white New Hampshire town. Albert Johnston, SB’25, MD’29, and his wife Thyra passed as white so that he could practice medicine in a job that would have been unavailable to him as a black doctor. Their four children grew up believing they were white. The Johnstons maintained the pretense for more than a decade, until one day in the early 1940s, when Albert Jr., home from boarding school, made an unthinking remark about a “colored” student there, and his father said, “Well, you’re colored.”

Hobbs chronicles those who passed as white at work in order to get better jobs and went home at night to black families in black neighborhoods. Hobbs calls it “nine to five passing,” although it required the passer to leave home before sunup and not come back until after dark to avoid being seen in their black neighborhoods. During the 19th century, African Americans sometimes passed as white in order to pass as free, using their light complexions to elude slaveholders and slave hunters.

Throughout the book, there are also those who refused to give up their blackness, despite straight hair and fair skin, who declined, as James Weldon Johnson famously worded it in the 1912 novel The Autobiography of an Ex-Colored Man, to sell “one’s birthright for a mess of pottage.” Robert Harlan, born to a slave woman and a white father—most likely the master—in Kentucky, grew up in the same household as the white Harlan boys and later went on as a free man to make a fortune in the California gold rush. He remained close to the other Harlans but never tried to take on their whiteness. One of his half brothers was Justice John Marshall Harlan, the Supreme Court’s “great dissenter,” who made the lonely argument for equality of all citizens under the law in the landmark 1896 case Plessy v. Ferguson.

A Chosen Exile grew out of Hobbs’s dissertation, and when she began her research, she says, “at first it seemed like I wasn’t going to get anywhere with it. Where were the sources going to be? Because people who passed obviously guarded their tracks and tried to leave no trace. It wasn’t like I could go into a library and find a folder. But I knew the sources were out there, because I knew there were stories like the one about this distant cousin of ours.”

Hobbs, who teaches American history at Stanford University, started by reading literature and going through the correspondence of Harlem Renaissance writers like Langston Hughes and Nella Larsen, picking out the gossip they exchanged about themselves and their acquaintances passing for white. “It was kind of this obsession or intrigue with them,” she says. But the crevice opened wider when she read the papers of sociologist E. Franklin Frazier, PhD’31. Frazier’s dissertation, The Negro Family in Chicago, became a groundbreaking text in the field. As a professor at Howard University, where he taught from 1934 to 1959, he asked his students to assemble family histories. Many of them, Hobbs found, reading his papers, couldn’t do it. “It was fascinating how many of the students really struggled,” she says. Relatives who’d passed as white and vanished from the family left wide gaps in the family tree. Sometimes one whole side would be blank. “They would say, ‘Well, I really don’t know much about this relative or that relative.’ Or, ‘I don’t know that much about my father’s side because this person passed as white and we never heard from them again,’” Hobbs says. “I was really struck reading these family histories and seeing all these examples of people who could barely tell the stories of their families.”

That’s when she began to see loss as part of the narrative. “I thought, I’ve really got to write about the people who were left behind,” she says. “Because they’re so much a part of the story. They’re often the ones who are describing the loss.” Later she thought again of her distant cousin married to a white man in Los Angeles, unable to come home to the South Side as her father lay dying. “What did she feel like when she hung up the phone?” Hobbs asks. “Her father was dying, she could never come back, she would never see her brothers again.”

Over the next decade or so while she worked on her dissertation and then the book, Hobbs suffered her own series of losses as people close to her died—the aunt who told her the story about the cousin and three first cousins who were like brothers and sisters to Hobbs. An uncle who was  an artist and spent long hours talking to Hobbs about the creative process. Her sister had died from breast cancer when Hobbs was 22. “That loss has always been a major, major part of my adult life.” As she waded deeper into her research and the aching narratives found there, she began to identify with the people she read about. She felt close to their pain; she almost grieved with them. “Obviously it’s a very different kind of loss, but passing is often equated with death,” she says. “And in many ways, it is.”

She doesn’t know what became of the cousin in Los Angeles. Hobbs’s father remembers visiting the family’s house once as a child and noticing “how light skinned they all were, the parents and the children, and she—this cousin—was the most light skinned.” Some years later, long after the phone call and the father’s death, one of the brothers died, and Hobbs’s father went to the funeral. But the cousin, of course, wasn’t there. “Those are the only fragments of that story that I have,” Hobbs says. Like so many of the people in her book, her own family tree has a gap.

One of the loved ones Hobbs lost helped spark her current book project, a study of the Great Migration through the experiences of travelers heading north through a segregated country. She plans to shed light on their journey by looking at the places where African Americans ate, slept, danced, where they stopped for gas or groceries or a hair cut or a bathroom break. An annual travelogue called The Negro Motorist Green Book: An International Travel Guide helped African Americans navigate their journeys with listings of tourist homes, hotels, boarding houses, restaurants, beauty shops, barbershops, nightclubs, and service stations where they would be welcomed. “When you talk to African Americans of a certain generation, everybody—everybody—can remember the difficulty they had, how hard it was to find a place to stay and a place to eat,” Hobbs says.

Her plan in part is to follow the Green Book. Traveling from New Orleans to Nashville, she found that most of the places listed in the guide no longer exist. “And that tells another story about black businesses and the decline of black businesses. It tells a whole story about the highways and the ways that the creation of the highways destroyed a lot of black neighborhoods.”

Like A Chosen Exile, it also tells a story about identity, the uncomfortable territory of in-between, about leaving home and self behind and setting out into something unknown. And like her first book, it also began with ambient anecdotes and a family story. Both of Hobbs’s parents came to Chicago as children during the Great Migration, her mother from New Orleans and her father from Augusta, Georgia. “My grandmother had told me incredible stories about the migration and moving to Chicago and her impressions of the journey,” Hobbs says. Her grandmother died just as she was finishing A Chosen Exile, but the stories stayed with her.