SAN FRANCISCO (KTVU) - Archaeologists for the National Park Service are closing in on the answers to a mystery 150 years in the making.
Four years ago maintenance crews in Fort Mason in San Francisco were working to transform an old hospital into housing.
Part of that work entailed cleaning lead paint out of the soil around the building. While digging out the contaminated soil, crews uncovered human bones.
National Park Service spokeswoman Alex Picavet said work came to a halt immediately. "It took a day to confer with the coroner, and with law enforcement to make sure that this was not a current scene," said Picavet.
After law enforcement decided it was not a crime scene, National Park Service archaeologist Leo Barker got to work at the site and made a grim discovery.
"It was a hospital from the 1860's and basically we found a large pit, it's called an ossuary pit," said Barker, "Which is a bone filled pit."
Weeks of work unearthed skulls, leg bones, arm bones, and vertebrae; 1,400 bones in all.
The bones in the pit were stacked by body part, but there was no complete skeleton from any one individual.
Archaeologist Barker says it was clear this was not a cemetery. "They were bones when they were placed in the pit itself," said Barker.
Archaeologists used clues to help date the site. Medicine bottles buried at the site were manufactured in the 1860's.
Given the dates involved Barker says Dr. Edwin Bentley, a doctor at what was then Point San Jose, likely collected the bones to use as teaching tools to help train new doctors. "They seem to be related to teaching; they seem to be related to examinations that took place for determining cause of death."
Barker says it appears new doctors who began using the building decided they didn't need to old teaching materials anymore, and simply dumped them in a hole in the backyard.
"The next set of surgeons was not interested in maintaining these curio cabinets that were the result of education and other activities," said Barker.
Analysis will continue on the bones and other material found in the pit - the hope is eventually the material will be made available online.