The National Geographic exhibition is called "Real Pirates," but the sprawling new show at Milwaukee Public Museum is more complex than the name suggests.

Of course, the focus is the story of the Whydah, a real pirate ship that's rested at the bottom of the sea, off the coast of Cape Cod, since it was sunk by a nor'easter on April 26, 1717.

But the three-masted, 300-ton galley called the Whydah – after the port of Ouidah in Benin – was built in Britain in 1715 as a commercial ship to carry slaves from West Africa to the Caribbean.

Suddenly, this is more than a Depp-style fantasy tale of swashbuckling buccaneers.

In a dark, evocatively presented space, the exhibition weaves together the diverse strands to tell the complex story of the slave trade and of piracy on the high seas and how those sinister activities intersected on the Whydah.

It was long known that the ship had run aground on a sand bar during a storm and lay in ruins beneath the waves. In 1984, explorer Barry Clifford located the wreckage, and he's been back to continue excavating the site ever since.

"Discovering the Whydah was the most exciting moment of my career," Clifford said.

"The sheer volume of artifacts the Whydah carried, from more than 50 other ships captured by the pirate Sam Bellamy and his men, provides a rare window into the otherwise mysterious world of 18th century pirates."

The items he's collected are spread throughout the exhibition to help tell the story. At the start, the ship's bell welcomes visitors. There are cannons, guns, shoes, jewelry, plates and cups, a needle used to brand the 700 slaves the ship could transport and a giant treasure chest overflowing with coins.

"(The show) is a chance to bring the real story of pirates to the public as it's never been told before – through real objects last touched by real pirates," said Clifford.

While the detailed explanation of how pirates worked, why they went over to the dark side on the high seas and how they lived is fascinating, what strikes visitors most is the early portion of the exhibition explaining the slave trade and the Whydah's role in it.

There are manacles, that dreadful needle and a branding iron that remind us of the brutal inhumanity of the trafficking in humanity.

"This was a unique period in our history," said Jeffrey Bolster, a professor of early American and Caribbean history at the University of New Hampshire.

"Through the cache of artifacts brought to the surface by Clifford and his team, we see a world generally undisclosed, one in which the Caribbean was the economic center and values were very different; an era before civil rights, before individual liberties and before democracy was institutionalized.

"Without the slave trade and the wealth of the region, piracy would not have existed. This is a story of the making of America – a true story more powerful than fiction."

Despite the heavy subject matter, the show is enjoyable, too, for its hands-on stations that allow visitors to try their hands at making sailors' knots of all kinds and touching original pirate treasure, and for the rocking ship that recreates the Whydah – the first fully authenticated pirate ship discovered in U.S. waters – on a grand scale.

A bevy of pirates roams the show, engaging visitors and adding another dimension to the experience.

"Real Pirates" is on view at Milwaukee Public Museum through May 27, 2013.