Up to 7,000 bodies have been found under the University of Mississippi Medical Centre's campus, which was formally the site of Mississippi State Lunatic Asylum.
Research teams used radar to check below the ground before they found the remains, buried in coffins, after unearthing 66 caskets back in 2012.
Doctor Molly Zuckerman, an associate anthropology professor at Mississippi State University, who is working with the Mississippi State Asylum Cemetery Project to uncover the bodies, told HuffPost the discovery will provide closure for families whose relatives have been missing for decades.
According to Zuckerman and the team, around 35,000 people were placed into the institution from 1855 to 1935, at which point it was relocated from its Jackson site to become Mississippi State Hospital in Rankin County.
And, despite the high number of bodies found, none of the deaths were 'particularly unusual'.
Credit: Mississippi Department of Archives and History
Advert
She said: "Mortality was very, very high in the asylum. Most died 13 months after they were institutionalised."
Patients died of strokes, heart attacks, TB as well as occasional epidemics. The doctor also added that nutritional deficiencies also led to deaths.
The bodies were likely to have belonged to patients whose families hadn't come to collect them, or those who weren't told in time to arrange a collection.
Although this happened a long time ago, Zuckerman said some families of former patients are still wondering what happened. She added she received two or three emails each week from the families of former patients asking her to look for their ancestors in the records.
Credit: University of Mississippi Medical Centre (UMMC)
Advert
She said: "Sometimes it's a straightforward exchange, other times we talk on the phone and I get to learn about the story that surrounds this ancestor, this lost ancestry. It's never a happy story. It's always tragic."
The team are hoping to exhume every one of the coffins, so they can identify who the person was, and eventually set up a memorial, visitor centre and genealogy facility.
Zuckerman said: "The people buried aren't just bodies, but can be turned into a tremendous resource for living people in the state.
"So that is one of the reasons why the goal is not just to remove them from the ground and rebury them, but to turn this into a unique resource."
However, the cost of exhumation and creating a research facility is not going to come cheap. Zuckerman it could cost about $21 million (£16.3 million).
Featured Image Credit: Lead image shows coffins being found in 2013. University of Mississippi Medical Centre (UMMC)