PROVIDENCE, R.I. (AP) — A project aimed at memorializing America's slave-trade ports is moving to Rhode Island, where some 1,000 slave-trading voyages were launched.

The Middle Passage Ceremonies and Port Markers Project has been working to place markers at 40 ports along the Atlantic and Gulf coasts where slaves arrived or where ships were sent to be used in the trade. The Middle Passage refers to the forced migration across the Atlantic Ocean of more than 10 million Africans, many of whom died on the way.

"We're just simply saying mark the place where it began," said Ann Chinn, who founded the Middle Passage project. "In the same way, people marked Plymouth, they marked Jamestown, they marked St. Augustine. Well, in each of those places, Africans were there too."

The project is rolling out as places around the country have been coming to grips with their roles in the slave trade, including the North, where the region's history of fighting against slavery is more widely known than its less noble roots of trading and profiting from slavery.

It uses the Voyages Trans-Atlantic Slave Trade Database at Emory University and other historical records to identify ports where slaves arrived or those that sent off ships used in the slave trade. Then, it works with local historical groups, churches and others to gain support to erect markers that note a city's role in the slave trade.

In some cases, local groups were already working on something similar. In Portsmouth, New Hampshire, for example, a group called Chinn in October to say it had already erected a granite marker saying slaves were brought there. Markers have also been placed in cities in Virginia, Georgia, Maryland, New York, Florida, South Carolina and Louisiana.

Each city works out the details on its own. Some markers contain just a few sentences. Others are several feet long and include maps and color illustrations. Markers can cost as little as $1,000, or several thousand for something more detailed.

One of the group's early efforts was in 2013 in Yorktown, Virginia, best known as the place where the British surrendered to George Washington, ending the Revolutionary War. At the time, there was little information about the history of slavery or African Americans at the site, even though it was a major slave trading port, said Lois Winter, who served at the time as chair of the Yorktown Historical Committee.

"They didn't include it as part of the tourist information, so people wouldn't know," she said.

Installing the marker, which details how Yorktown served as the primary point of entry for Africans brought to Virginia, means visitors are now learning a more complete history, Winter said.

"You're ignoring this huge chunk of population by not including them in the story," she said.

Around 60 percent of all slave-trading voyages launched from North America came from Rhode Island, according to a Brown University report issued in 2006. Voyages left from Providence, Newport, Bristol and Warren. More than 2,700 slaves were brought directly to Rhode Island, according to the Voyages database. In addition, the state's economy was built on the trade, including shipbuilding, rum distilleries and other industries.

People from Brown University and other local groups plan to meet Friday to discuss how to move forward. Ray Rickman, who is deeply involved in local historical endeavors, said he especially wants to see a marker in the tourist hub of Newport, where millions of people visit every year. According to the Brown University report, Newport's streets were paved with money generated from a duty on slave imports.

Rickman said the nation could begin to fix its racial problems if people knew more about its history.

"There are some real positive things that could come out of a very close look at this," he said.