New Jersey’s role in the Atlantic slave trade has been documented in scholarly papers, websites, and even in the state’s own records.

But a new book published by Rutgers University Press provides a startling illustration of the state’s past.

Readers of Mapping New Jersey can see where slaves were held in the state during the year 1798, and learn about the connection between slave-holding activity and church affiliation.

Simply put, several swaths of northern New Jersey, with numerous Colonial Dutch churches, had the highest concentration of slaves. At the same time, there were far fewer slaves in the southwestern areas near Pennsylvania, where Quakers were prevalent.

“Many people don’t realize that New Jersey was a slave-holding state, but it was,” said Peter O. Wacker, co-editor of the book and an emeritus professor of geography at Rutgers. “And there were great religious differences over slavery in the population.”

The book, subtitled An Evolving Landscape, is an interpretive atlas that illuminates the state’s transformation from simple farming communities to a crowded, ethnically diverse, post-industrial society. Michael Siegel, a cartographer in the Department of Geography, created the book’s maps.

Although the map showing the slave population is just one small portion of the book, it reflects the overall aim of the project, said Maxine Lurie, who served as co-editor.

“We were trying to create maps that didn’t exist,” said Lurie, a professor of history at Seton Hall University, who taught part time at Rutgers for many years. “We knew, for example, that there were more slaves in East Jersey. But when you see it on a map for the first time, it’s really dramatic.”

At one point in time, New Jersey had as many as 12,000 slaves. And while it passed a gradual emancipation law in 1804, it was the last Northern state to free its slaves, according to a resolution passed by the Legislature in 2008 that apologized for the state’s role in the slave trade.

Although the Dutch were not the only ones holding slaves, the map makes it clear that the practice was especially prevalent in the Dutch settled areas of northern New Jersey.

“The Dutch were very canny farmers and the extra labor supply really helped them out,” Wacker said.

The Quakers, however, abolished the practice at about the time of the Revolution.

“They said not only is slavery wrong, but if you keep slaves, you cannot be a Quaker,” Lurie said.

Wacker said the statistics on slaves were obtained through federal tax assessment records from 1798. He credited the work of a private researcher, Judith Green Watson, with making those records available.

Both Wacker and Lurie noted New Jersey’s role as a slave state isn’t well known among laypeople.

“My students are usually surprised,” she said. “They consider it a Southern institution.”