Soon after the British took Charles Town in 1780, they locked up a local trader in the Exchange Building cellar.

If you go

The Old Exchange Building and Provost Dungeon is open every day from 9 a.m. to 5 p.m.It is located at 122 East Bay St., CharlestonAdmission is $8 for adults, $4 for students and children ages 7-12. Children under 6 are admitted freeFor more information, call 727-2165Michael Coker will give a lecture on the new findings about provost prisoners of war at 6 p.m. Sept. 12. Admission is free, but patrons are asked to consider a $3 donation.

Casper Strobel’s only crime was that his two sons were fighting for the “rebels.” In retaliation, the 63-year-old Strobel was detained at the Provost Dungeon, where he “remained in chains until insensible.” And then he was released.

He died the next day.

It is part of Charleston legend that the Old Exchange Building served as the British’s “provost dungeon” during the Revolution, but details have been as scarce as 200-year-old records. The story has been told through family lore and mentions in old histories. But there was no official prisoner list — until now.

The Old Exchange Building and Provost Dungeon has just finished a yearlong research project to investigate the landmark attraction’s days as a British prisoner-of-war jail. While it is probably impossible to compile a comprehensive list of prisoners, this is the most complete yet assembled. The results of this work shed new light on an often overlooked period of the city’s history.

Some people were held for mere hours before they were taken to other jails or prison ships; others spent months at the foot of Broad Street. There is no accounting of how many people died behind its walls, but there were certainly several.

One local man, Robert Stark, wrote of “the heat, darkness of the place, and want of water” that plagued him and other prisoners.

These prisoners ate soldier’s rations, and one account holds that the daughter of a patriot gunsmith sneaked her father rice through the bars of the cellar windows.

In all, the Old Exchange Building has identified 120 South Carolina residents or patriots who spent time as prisoners on site under the charges of treason or sedition.

And they weren’t all kept in the “dungeon,” which was a term used by occupants.

“The whole building was a provost,” said Tony Youmans, director of the Old Exchange Building.

In the spring of 1780, the British began a six-week siege of Charles Town, the longest of the Revolutionary War. They tried to take the city in 1776, only to be repelled by troops on Sullivan’s Island. This time they would not give up so easily.

Soon after Gen. Benjamin Lincoln surrendered the city on May 12, the British took the Exchange Building — not even a decade old at the time — and began to use it as a place to lock up local criminals and insubordinate British soldiers. Records of the time show that one British soldier spent five days in the provost for the crime of “beating a negro in the streets.”

Other Redcoats were jailed for plundering.

Soon the provost became a place to lock up local patriots — among them Declaration of Independence signers Arthur Middleton, Edward Rutledge and Thomas Heyward Jr.

Many of these men were transferred to a prison in St. Augustine, Fla., to thwart their efforts to communicate with patriots in the backcountry of South Carolina. A few, including Middleton, were paroled with the understanding that they would no longer engage in rebellious activity.

Basically, the British didn’t have enough room to lock up everyone.

“It is an untold story of the Revolutionary War in Charleston,” said Carl Borick, author of “Relieve Us of This Burthen: American Prisoners of War in the Revolutionary South, 1780–1782.”

“It just highlights how rebellious South Carolina was during the Revolutionary War.”

Borick, assistant director at the Charleston Museum, helped Old Exchange Building staffers Youmans and Michael Coker with the research, along with Mary Edna Sullivan at Middleton Place and Karen Stokes at the S.C. Historical Society.

The research was funded by the “Friends of the Old Exchange” and local resident Paul “Sonny” Marshall donated money for a large, new exhibit on the prisoners of the provost.

Marshall’s ancestor Maj. Thomas Grimball was among the prisoners held in the provost. He was transferred to St. Augustine but remained loyal to the cause, donating 80,000 pounds to the South Carolina government to continue operating during the war.

Many of the provost prisoners who were released, or even signed paroles, continued to aid the colonists’ cause. One of those was Lt. Col. John F. Grimke of the 4th South Carolina.

Grimke was held with other soldiers at Haddrell’s Point in Mount Pleasant, but at one point, was moved to the provost. He considered the move, with its less accommodating food and lodging than Mount Pleasant, a violation of his parole and took up fighting again.

The British didn’t see it that way, Borick said, and spent the rest of the war looking for Grimke for violating that parole.

In December 1782, the British evacuated Charles Town and the building was converted to storage space.

For two centuries, it has held much of Charleston’s history in it. And now some more of it is on display daily at the museum.

Officials there say, however, there is still much to learn.

“There are hundreds of other prisoners, we just don’t know who they are,” Coker said. “This is just a small fraction.”

Reach Brian Hicks at 937-5561 or follow him on Twitter at @BriHicks_PandC.