Outside the city on a broad hillside, thick with green underbrush and shaded by poplar trees, Sam Ricks hacks through tangled knots of weeds with his machete - leaving no stone unexamined in his quest to identify the dead.

Ricks is leading an effort to locate Medal of Honor winners and hundreds of other long-forgotten Navy and Marine veterans buried in Mount Moriah Cemetery, the historic, abandoned graveyard that straddles Philadelphia and Yeadon.

Its 21 medal honorees may be the most buried in any cemetery in the country, according to a military expert.

"After it was first abandoned, I drove through and it looked like the opening scene of Bridge on the River Kwai - a jungle overgrown with weeds," said Ricks, a volunteer with the Friends of Mount Moriah Cemetery.

In less than two years, Ricks has found and identified four Medal of Honor recipients and seven African American veterans from the Civil and Spanish American Wars in the graveyard's Naval Asylum Plot.

The plot is one of two military grave sites overseen by the Department of Veterans Affairs in the cemetery. Though the VA maintains the grave sites, volunteers clear overgrown pathways so visitors can get to the military plots.

Ricks bent over to point out what at first glance appeared to be an ordinary flat, gray marker in the grass, backed by a white marble headstone with the word Unknown.

Thanks to volunteers' efforts, the grave's occupant is now known: Commodore Jesse Duncan Elliott, a hero of the War of 1812 and Medal of Honor winner for his bravery in the Battle of the Great Lakes, 200 years ago this month.

"The VA said he was here but didn't know where," explained Ricks, who discovered through research that Elliott's grave had been marked with a plain flat stone, then in 1900 by six surrounding stanchions.

"The only one around here is this," he said, relishing arguably the most famous of the roughly 130 veterans whose burial markers the project has identified within the Naval Asylum Plot. He does not rest on those achievements, since the best records suggest that about 2,300 Navy and Marine vets - from the American Revolution through Vietnam - are buried in the area.

Don Morfe, a researcher with the Medal of Honor Historical Society, said the 21 known recipients are probably the most for any cemetery, and he suspects Ricks will eventually turn up more. Now he is trying to get the VA to erect Medal of Honor markers for the four honorees that Ricks has found, "but so far they haven't made any move," he said.

There are a number of cemeteries across the state with similar stories to Mount Moriah - largely forgotten and in some cases officially abandoned, overrun by weeds and havens for vandalism, illegal dumping, crime, even packs of wild dogs.

But officials say Mount Moriah is unique. Once the largest graveyard in Pennsylvania, with 380 acres behind a grand Romanesque entrance, it was also the final resting place for Betsy Ross and her third husband before they were moved to a courtyard at the Betsy Ross House in 1976.

After the cemetery was abandoned in 2011 by the widow of the last known member of its governing association - a man who had died seven years earlier - local activists formed to organize volunteer cleanups, seek restoration funding, and call attention to the rich history of the burial ground.

The effort was a natural for Ricks, 59, who lives in Philadelphia and is retired from the trucking industry. When his late twin brother learned that an ancestor had served in the Confederate army, Ricks not only joined the local Sons of Confederate Veterans but became a tombstone detective, helping find about 250 veterans of the Lost Cause in Philadelphia cemeteries.

Shortly after he joined the Mount Moriah committee, Ricks was contacted by a historian from Eden Cemetery in Collingdale who was looking for a relative of James Forten Dunbar, believed to have been the longest serving African American in naval history, enlisting in 1811 and serving through the Civil War.

Ricks was able to find Dunbar's marker - the name had almost completely faded - but he was also surprised to learn the extent to which naval burial records were inaccurate or incomplete, and that time had nearly worn many of the headstones almost beyond recognition.

"These stones are going blank right before our eyes," said Ricks, standing next to Dunbar's grave marker. "We can't let them go to Davy Jones' locker, as they say at sea."

"It's like a giant jigsaw puzzle with 2,300 pieces," he explained. "If you find one and it matches the plot and row and grave, you can count back from there."

A walk through the tract with the amateur historian is rich with snapshots of U.S. naval history.

He stops at the final resting place of William Henry Scholls, who joined the Confederate army as a 13-year-old drummer boy in 1861 and lived long enough to volunteer for naval duty during World War I, dying in a Philadelphia veterans' hospital in 1931. "This is a rare grave - one we can prove with Confederate records," he said.

A small, barely readable marker shows where Thomas Johnson, a seaman who fought with the legendary John Paul Jones - "I have not yet begun to fight" - on the Bonhomme Richard against the British in 1779, was laid to rest. "Johnson was the first Revolutionary War sailor that we found," Ricks noted.

The Friends of Mount Moriah is organizing events, such as a Restoration Day this Saturday that will include cleanup volunteers from Villanova University, and is working to identify more African American sailors. Ricks' words show a determination to leave no man unmarked.

"The last mile," he said of his searches, "is always the hardest."

kboccella@phillynews.com 610-313-8232 @kathyboccella