A Rice University-led consortium uses Oracle Cloud to give researchers a better understanding of the Atlantic slave trade

By using data to examine this painful history, researchers involved with the SlaveVoyages project shed new light and raise key questions.

By Mark Jackley | February 2022

Not so long ago, historians worked with a different set of facts about the slave trade that existed across the Atlantic from about 1500 to well into the 1800s.

For example, it was commonly thought that the United States (and the British colonies before the union) brought in nearly as many enslaved Africans as any other nation. It was also believed that while enslaved people were numerous in the Americas, they were a fraction of the people who came here from other countries. In any case, some historians concluded that by the time the 13 American colonies won their independence in 1783, the slave trade was in a natural and inevitable decline.

Wrong, wrong, and very wrong.

Thanks to the SlaveVoyages project—home to the world’s largest repository of data about the Atlantic slave trade, with databases recently moved to Oracle Cloud Infrastructure—historians have updated the facts, including:

Portugal’s colonial empire imported 10 times more enslaved persons than the US, mostly to Brazil. Less than 4% came directly to the US, totaling more than 388,000.

For every European that came to the Americas before 1820—arriving in New York, Charleston, and other ports along the US eastern seaboard, plus harbors throughout the Caribbean and South America—four Africans arrived to suffer a life in bondage.

Right up until the slave trade was abolished in 1808, the number of slave voyages increased. The business of slavery was growing, not shrinking. Indeed, illegal slave trading continued for decades.

The story of the slave trade is partially told in numbers, though the numbers often supply more questions than answers. That’s fine with the experts who manage the SlaveVoyages project, who are making history by changing our understanding of history—shifting the way their peers, and ultimately the public, understand a complex, deeply emotional subject.

“Our goals are to understand the history of the slave trade better and make this information more accessible to the public,” says Dr. Daniel Domingues da Silva, an associate professor of history at Rice University, who has researched slave voyages for over two decades. “So many of the topics people have heard about—slave ships, resistance to slavery, or which nations were involved—can now be researched online. People can look them up.”

Slaveship manifests

The names of more than 95,000 enslaved persons are contained in The African Origins Database, which is part of the SlaveVoyages project.
View larger images of the original document and the database.

A significant research project

Located at SlaveVoyages.org and hosted by Rice, the project has created databases on the Trans-Atlantic slave trade, the Intra-American trade, and the People of the Atlantic slave trade. SlaveVoyages is managed by a consortium of institutions: Emory University, where the project began, Rice, Harvard University, the Omohundro Institute of Early American History and Culture at the College of William & Mary, three campuses of the University of California, and the National Museum of African American History and Culture.

Dr. David Eltis, professor emeritus of history at Emory, started working with colleagues in the 1960s to gather data from slave ship logs, port records, and other sources scattered around the world, and eventually moved it over the years from punch cards and floppy disks to CD-ROMs then servers and now a cloud database.

Harvard Professor Henry Louis Gates Jr., director of the school’s Hutchins Center for African and African American History, and host of the PBS show Finding Your Roots, calls SlaveVoyages “one of the most dramatically significant research projects in the history of world slavery.”

In September 2021, 77,000 people visited SlaveVoyages.org, and not all of them are historians. The site is open to students, genealogists, and anyone else curious about the buying, selling, and exploitation of human beings for profit.


“The statistics really should raise questions. You have to understand why and how things happened.”

Dr. Ugo Nwokeji, Associate Professor of African American and African Diaspora Studies, the University of California, Berkeley

New numbers, new stories

Asked about SlaveVoyages’ impact, Dr. Eltis quotes Hans Rosling, the late Swedish health expert and data visionary: “The world cannot be understood without numbers. And it cannot be understood with numbers alone.” Dr. Eltis adds that the project “has gone some way in striking the right balance.”

For example, in Dr. Eltis’ view, before the early 1800s the Americas were an extension of Africa, not Europe, given that three of four newcomers were enslaved Africans. That wouldn’t change until mid-century, when European immigrants, such as Irish fleeing the potato famine and Germans escaping political turmoil, began to arrive by the millions.

Over the 300-plus years of the Atlantic slave trade, there were more than 36,000 slave voyages from Africa to the Americas, what’s known as the Middle Passage. About 12.5 million Africans were crammed onto ships, and some 1.8 million died en route. Portugal transported 5.8 million, mostly to Brazil to toil on sugar plantations, and Great Britain took 3.3 million to Caribbean colonies as well as to North America. While Brazil brought in many more enslaved people than North America, the US enslaved population grew dramatically while Brazil’s and the Caribbean’s declined due to death from disease, climate, and other factors there. By 1860, the total American enslaved population was approximately 4 million, by far the most in the Americas, many working on cotton plantations.

Behind the data, people

As Dr. Eltis noted, numbers don’t tell the whole story. Dr. Ugo Nwokeji, associate professor of African American and African Diaspora Studies at the University of California, Berkeley, agrees. “There has been a tendency for people to present statistics as if they answer questions,” he says. “The statistics really should raise questions. You have to understand why and how things happened.”

Dr. Ugo Nwokeji, Associate Professor of African American and African Diaspora Studies, the University of California, Berkeley, has made extensive use of the SlaveVoyages database.

Dr. Marcus Rediker, author of several books on the slave trade, pointedly titled one of his books The Slave Ship: A Human History. “It’s essential that we understand this as a human, or shall we say, inhuman system,” he says. “One of the dangers of statistical history is that it can sanitize the past. There’s something called the violence of abstraction, in which it’s possible to forget that these were real people on board, suffering extraordinary violence.”

In writing his books, Rediker, a Professor of History at University of Pittsburgh, has relied on SlaveVoyages data to supplement or cross-check other historical sources. To translate such data for a broader audience, Rediker turns to storytelling.

One of his books, The Amistad Rebellion: An Atlantic Odyssey of Slavery and Freedom, recounts how enslaved Africans took control of the Spanish schooner Amistad and sailed to eventual freedom in the US. Made into a movie by Steven Spielberg, the tale of the Amistad humanizes a key data point: 1 in 10 slave voyages experienced a rebellion, though most were unsuccessful.

Rediscovering Africa

Another way SlaveVoyages helps humanize the past is by revealing more about the African people subjected to the terror of slavery.

The African Origins Database, which is part of the SlaveVoyages project, contains more than 95,000 names of enslaved persons found in legal records, which were compiled in the decades following the slave trade’s abolition. To enforce treaties outlawing the trade, the British navy seized slave ships and, to the best of their ability, recorded captives’ names.

Bora, Flam, Dee. Muffa, Latty, Trua. Who were they? What were their stories? In most cases, we’ll never know. Slave traders wrote down some names, but most are lost to the ages. The surviving names, however, resonate powerfully.

“Where I am most moved is in the very human reactions of either African Americans or people in Africa,” says Dr. Nwokeji, who hails from Nigeria. “They are blown away by just being able to see them, often names that are their own. They see something of themselves.”

Taking the past back to school

The experts behind SlaveVoyages are teachers as well as historians. Besides teaching college students and directing graduate research, some of them advise high schools on their history curricula, occasionally visiting classrooms.

Dr. Nafees Khan, assistant professor of Social Foundations at Clemson University, serves as the project’s curriculum development advisor. A specialist in history and social studies education, he frequently works with high schools, and sometimes middle and elementary schools, on teaching the slave trade and the larger topic of slavery.

Numbers that spark discussions


slave voyages

10.7 million

captives survived the journey

Over 5 million

enslaved persons shipped by Portugal to Brazil


enslaved people taken to the US, both directly from Africa and from elsewhere in the Americas

3 of 4

arrivals to the Americas before 1820 were African

He finds that students are hungry to learn. “I start with basic data like 12.5 million captives shipped and 10.7 million surviving,” he says. “The numbers frame the discussions and trigger a lot of questions. ‘Wait, where did they come from? Which civilizations were there? Who was trading and why?’ Their questions sometimes guide the teachers, which is really encouraging.”

Dr. Khan says his discussions with Black students are especially poignant. When students learn where their ancestors came from, regionally at least, and all the places they were shipped to, they see communities torn apart and re-forming at global scale.

“Some of our conversations are about cultural identity,” he says. “We talk about hair and music and family and the ways we communicate, and they learn there are similar conversations happening in, say, Cuba and Jamaica. They never realized how much they have in common with people who live in other countries and speak different languages.”

Focusing more on the African diaspora could, in Dr. Khan’s view, help correct a weakness in high school textbooks. “Typically, textbooks go straight from the Middle Passage to Harriet Tubman and MLK’s ‘I have a dream.’” This focus on extraordinary lives tends to leave out the millions who struggled, suffered, and resisted in their own ways.

Questions, questions

Dr. Domingues stresses that the slave trade is an inherently difficult topic, both in its complexity and the horrors it presents. He adds the US isn’t the only nation coming to terms with its past.

“We are dealing with it in Brazil, my native country, and there are communities in Africa doing the same thing,” he says. “In Africa, the conversations have less to do with race and more with how the slave trade gave certain groups social advantages.”

One thing the experts agree on: the importance of remaining curious and following the evidence. “The SlaveVoyages project has definitely raised awareness,” says Dr. Nwokeji. “I get email from people who are not historians. They have a lot of questions.”

Oracle for Research is on a mission to partner with academic, educational, and institutional researchers in all aspects of discovery. At our core, we believe researchers shouldn’t be held back by tech, which is why we’ve made it simple for them to host, store, and analyze their data with our cloud infrastructure solutions. Our research customers are changing the world—and we’re proud to help them do it.

Images: Courtesy of SlaveVoyages.org

Mark Jackley

Mark Jackley

Mark Jackley is a brand copywriter at Oracle.