Excavations in Massachusetts, New Jersey and New York have unearthed evidence proving some large estates in the north had black slaves in the late 1700s and early 1800s.
James Cobb, University professor of history, said although the discovery is interesting, it is well known that "lots of northerners" were involved in the slave trade.
"These kinds of reminders are important to understand the roots of the racial conditions are not necessarily totally southern," he said.
Cobb said the discovery of the northern plantations should not take away from the importance of what happened in the past.
Excavations near Salem, Mass. found evidence at least 100 black slaves worked on Samuel Browne's plantation producing grain and dried meat, and raising horses.
The main reason slavery did not become as entrenched in this society as it did in the south is an economic one, Cobb said.
Crops grown on southern plantations -- such as tobacco, rice and cotton -- are labor-intensive and suited to the southern climate.
"It's not a situation where white southerners were inherently more racist to start with," he said. "It's just that slavery became much more of a fixture in the agricultural society."
In the North, the land and climate were not as suitable for agriculture, which led to an industrial-based economy.
The differences in economic systems, however, does not lead to differences in values, Cobb said.
"There's no particular reason to think that in the early 17th century the views white southerners held for blacks were any difference than the views of the people who would have been in New England," he said.
"It gives a better sense of how slavery was able to flourish in a new country supposedly dedicated to human equality and liberty."
Cheryl LaRoche, a historical archaeologist at the University of Maryland, told the Atlanta-Journal Constitution that historians are stunned by some of the evidence.
"The popular notion is that slavery in the North consisted of two or three household servants but there is growing evidence there were slaveholding plantations," she said. "It's hard to believe that such a significant and pervasive part of the past could be so completely erased from our history."
-- Contributing: The Atlanta Journal-Constitution