A flag marks what is thought to be a headstones at the spot in Crownsville, Md., archaeologists believe to be a slave burial ground on the site of the Belvoir plantation. (Jonathan Newton/The Washington Post)

When Nancy Matthews Daniels was growing up in Laurel, Md., her grandmother used to tell stories about their ancestors, including some who had been slaves “down in the country.” Daniels, 69, grew up to be a genealogy enthusiast and researched her relatives, some of whom were involved in the Underground Railroad and served prison time for helping slaves escape.

It turned out that “down in the country” referred to Belvoir, a large tobacco plantation in Crownsville, near Annapolis, owned by relatives of Francis Scott Key and active during the 18th and 19th centuries. In 2014, remains of slave quarters were discovered on the site, now owned by a private school, and through that project Daniels ended up connecting with other descendants of Belvoir slaves. Archaeologists found crockery, buttons and other items belonging to those who had lived there. But one thing was missing: the ancestors themselves. What had happened to them when they died? Where were they buried?

Two weeks ago, they got what is very likely the answer.

“Julie called and said they found the cemetery and she wanted us down there,” Daniels said, referring to Julie Schablitsky, chief archaeologist with the Maryland Department of Transportation’s State Highway Administration.

A couple of men who had played in the area as kids in the 1970s heard about the slave quarters and the mystery of the burial ground and remembered a particular spot in the woods where a marble headstone lay. They contacted Schablitsky.

She gets these calls from time to time, ever since the slave quarters were discovered as part of a years-long state survey of Maryland Route 178, also known as Generals Highway. Schablitsky always follows up, though the reports usually lead to nothing. But when she followed the men down a trail heading away from the old slave quarters, the site seemed ideal.

It was an elevated promontory of forest, surrounded by old trunks of cedar trees, which are often associated with cemeteries. After the leaves and sticks were cleared, jagged tops of about eight fieldstones — often used to mark the burial spots of slaves — jutted out of the earth at regular intervals. Two halves of a marble slab the size of a gravestone lay on the site, so weatherworn that any words etched into it are long gone. And near one tree, a rectangular depression in the earth faced east to west, as graves often do.

Other signs pointed to this being the spot. It is an uneven hillock, not suitable for building or farming; slave burial grounds were often in such out-of-the-way, unusable areas. And it was a straight shot from the slave quarters, short enough for a funeral procession that wouldn’t take slaves away from their work for too long.

Even without scientific proof, the facts seemed to point strongly in the right direction.

Then on Feb. 24, a group including Schablitsky, five descendants of Belvoir slaves and one of the local men who had identified the site met there to see how a team of three cadaver-sniffing dogs would react.

“The black Lab came running out, and as it hit the cemetery it stopped in its track like it hit a wall,” Schablitsky said.

And the spot with the indentation? All three dogs lay down in it.

Watching them, one of the descendants, Shelley Evans, 67, of York, Pa., felt tears well up. “I was just in awe. I held my hand over my mouth,” she said. “I mean, maybe some of my ancestors were buried there.”

Of the old plantation site, once several thousand acres, much has been sold and developed. The remaining 144 acres belong to the Rockbridge Academy, a private Christian school that maintains the property and sometimes uses the archaeological findings to supplement lessons on colonialism.

Schablitsky estimated there could be several dozen people buried there from 1736 to 1864, when slaves were emancipated in Maryland. The broken marble headstone could belong to a 4-year-old African American boy, Joseph Grocia, who was buried somewhere on the Belvoir property in 1913, Schablitsky said.

To Janice Hayes-Williams, a historian and columnist who specializes in African American Annapolis, the finding represents a crucial unpeeling of the onion layers of history.

“A lot of us as African Americans, there’s no identifiable landmark to say that we were there,” she said. “We hear that our great-grandfather was on the inventory of such and such a person. We know where we are from, but we don’t know where our family was buried. . . . We weren’t allowed to read or write, so how do we record? In my opinion this is significant to prove that we existed. If you’re not African American, descended from slaves, you can’t sense the need for us to understand from whence we came.”

Many of the families from the Belvoir plantation era still live in the area, Hayes-Williams said. “It’s like our ancestors arriving from the ground to tell our stories,” she said, “to tell us we were here.”

One particularly wrenching story associated with Belvoir is about a slave who lived there named Cinderella. She was around 22 and married to a free black man named Abraham Brogden.

In December 1848, he learned she was going to be sold. He helped her escape, and the two fled to Baltimore but were quickly apprehended. He was sentenced to five years in prison, and she died before the end of December.

The cause of her death is unknown, but “I guess you can surmise what happens to a runaway slave,” said Pam Brogden, 64, a Hanover, Md., woman who believes she may be related to Abraham or Cinderella. (Cinderella and her sister Eliza had the last name Brogden, possibly through marriage.)

“There’s a possibility that Cinderella could be buried there,” Brogden said. “It was just a warm feeling that, wow, after all these years, wow.” Her voice broke, and she let out a sob. “Because a lot of times it’s just difficult for black people to go back that far. . . . I think of that song, ‘Before I be a slave I’ll be buried in my grave,’ and every time I hear that song I get really emotional because I always think of Cinderella. She tried. She tried to get away.”

On Friday, several descendants and others associated with the find returned — including Daniels, who brought along a large pill bottle to fill with soil from the site.

“I took some of this to bring over to the cemeteries in P.G. County,” she said, referring to the graves of relatives. “And I’m going to take a little to sprinkle around my garden. This is a sacred spot.”

Rodney Daff, 50, one of the men who found the spot, was there, too. He said the elders of his family had long known about it. “My cousin used to come back here and squirrel hunt,” he said. One day, as the cousin looked for something to put out a cigarette, he came across a stone. “He told his father, and my uncle said, ‘It’s the slave cemetery.’ Then, when I read that story about the slave quarters and I heard they were looking for it, I said, ‘I think I know where that is.’ ”

There are no immediate plans to do anything with the site other than protect it, Schablitsky said, though in the future there could be some analysis of what lies under the soil if descendants are in agreement.

For now, just standing there was a big deal. “To me it’s the most exciting thing other than the birth of my son,” said Wanda Watts, 65, of Baltimore, who is a sister of Evans and, as she has learned, a distant relative of Daniels through their Belvoir history. “It gives me a feeling of peace because we know they weren’t just tossed away or put in unmarked graves somewhere on the property. We know there was some reverence, that they were people.”

Daniels clutched her vial of soil in the thin winter light. “To see this right here, if I was on my dying bed I’d get up and come,” she said, gesturing at the burial site. “Looks to me our past is coming together.”