Archaeologists have found the remains of a 19th-century hospital and cemetery underwater off the coast of the Florida Keys, officials shared this week.

The wreckage of a small quarantine hospital and the surrounding graves were found on a submerged island off Dry Tortugas National Park on Garden Key, the National Park Service announced on Monday.

The hospital was used to treat yellow fever patients at nearby Fort Jefferson between 1890 and 1900, the agency said.

The cemetery is believed to be the Fort Jefferson Post Cemetery, where historical records indicate that dozens of US soldiers may have been buried.

So far, only one headstone belonging to laborer John Greer, who died in Nov. 1861, has been positively identified. One image included with the NPS statement shows University of Miami graduate student Devon Fogarty examining the large greywacke slab.

The NPS confirmed that the fascinating under-the-sea find was part of a survey by park staff, members of the Submerged Resources Center, the Southeast Archaeological Center, and Fogarty.

“This intriguing find highlights the potential for untold stories in Dry Tortugas National Park, both above and below the water,” Joe Marano, a maritime archaeologist and the survey’s project director, said in the statement.

“Although much of the history of Fort Jefferson focuses on the fortification itself and some of its infamous prisoners, we are actively working to tell the stories of the enslaved people, women, children and civilian laborers.”

While most famous for its pivotal role in the Union’s shipping blockade during the Civil War, Fort Jefferson has a lengthy history as an important outpost for ships in the Gulf of Mexico and the Straits of Florida.

Despite its key location, however, the fort was never fully armed or finished. It was abandoned by the military in 1874, and later served as a coaling station for warships.