— When genealogist Agnes Kane Callum made her first visit to Sotterley, the sprawling St. Mary's County plantation where her great-grandfather lived as a slave, she was surprised to learn that the tour included no stops at the 1830s-era slave cabin that stands down the hill from the main mansion.
In fact, when Callum, a Baltimore native who spent decades chronicling Maryland's African-American history, insisted on seeing the building, she found it locked with a "DO NOT ENTER" sign across the door.
"For many years, the prevailing sentiment was 'Let's leave that whole subject behind; it's too difficult,'" says Nancy Easterling, director of Historic Sotterley Inc., the nonprofit that operates the 94-acre site as a living monument to the past.
Callum died at age 90 in 2015. Sotterley Plantation officials will honor her life's work Friday when they open the one-room wooden structure as a permanent walk-through exhibit.
At a ceremony expected to attract about 200 people, officials of the National Historic Landmark will dedicate the cabin to Callum, an obsessive researcher who argued that the history of slavery should be studied and shared in all its details, not soft-pedaled or avoided.
After her initial visit, Callum spent years bringing relatives, friends and students to Sotterley by bus (it's about a two-hour drive from Baltimore), then giving impromptu talks at the cabin, frequently relating stories about the lives of enslaved people she had heard from family members.
By the early 1990s, when she became the first African-American member of the museum's board of directors, the nonprofit was allowing visitors to enter the cabin on request.
Over the past half-decade, Easterling says, officials have attracted sufficient funding to support a restoration, including signage that tells the story of the cabin and its inhabitants as Sotterley researchers have pieced it together.
One of those researchers, education director Jeanne Pirtle, stood on the dirt floor inside the building one afternoon this week and gestured to the artifacts that bring the space to life — a rough pallet of the kind inhabitants would have slept on, replicas of the fish and fatback slabs they would have eaten, a rough-hewn ladder that leads up to a stuffy loft.
The cabin measures 16 feet by 18 feet, no bigger than the kitchen in some modern homes.
Between nine and 20 people people lived in it at a given time — about the same number, Pirtle says, that usually lived in the slaveholders' mansion a few yards away.
Guests used to say it was amazing to hear that so many people lived in the main house, she says, then be thunderstruck to learn the same was true of the cabin.
Callum's passion for revisiting the era of slavery didn't always meet with approval, particularly in the African-American community.
She was often told such a disgraceful and painful chapter of history was beneath remembering.
Callum never wavered, arguing that African-Americans' enslaved forebears lived real lives, earnestly and courageously, and that their stories should be shared — in part to honor them, in part to ensure that no one would ever live under such conditions again.
Easterling, who became executive director in 2009, says Callum's views eventually gained traction at an institution that, like others of its kind, had long avoided addressing the uglier side of its past.
So much of the history of enslaved people has gone unrecorded, she says, that versions of the past as told by the slaveholding class held a disproportionate influence, a imbalance it has taken scholars like Callum decades to rectify.
Over the past 10 years or so, Easterling says, Sotterley has reconfigured its mission with programs that relate its 318-year history as an "integrated" story.
The "Land, Lives and Labor" exhibit it opened in a former corn crib in 2015, for example, includes lists of the names of hundreds of enslaved persons who lived on the plantation, many of them culled from the "property" records of those who owned the place.
"The Choice," a living-history drama Sotterley offered last year, used actors to bring to life a little-told chapter of plantation history: During the War of 1812, 49 of the 64 enslaved people who lived there escaped to join the British side.
Scenes were set both at the plantation house and in the slave quarters, allowing views of the war from multiple points of view.
Visitors to the site — and more recently to its website — can view a video version of the play.
A "Slavery to Freedom" tour of the grounds and its 20 historic buildings also shares multiple perspectives. And a "Women of Sotterley" presentation incorporates not just the day-to-day details of the lives of the white women who helped run the plantation, but also those of the enslaved women who did laundry, cooked and cared for children.
The cabin opening comes 45 years after Callum's first visit. Officials say they would probably have taken the step years ago had they not been faced with two formidable obstacles: the cultural entrenchment of a more sanitized version of its history and a dearth of funding that continues to this day.
Subsisting without government support, Sotterley relies on grants and other private support.
Sotterley's last private owner, Mabel Satterlee Ingalls, created the Historic Sotterley Plantation Foundation and opened the site as a museum in 1961, but left almost nothing in the way of funding upon her death in 1993.
Three years later, a descendant of one of its enslaved families — along with a descendant of one of its former owners — stepped in.
John Hanson Briscoe, a former St. Mary's County Circuit Court judge who served as speaker of the Maryland House of Delegates in the 1970s, was a longtime advocate of historic and environmental preservation.
His ancestor, Walter Briscoe, had owned Sotterley — and dozens of slaves, including some of Callum's forebears — for more than 50 years during the 19th century. When the historic site was threatened with closure, he decided to act.
He and Callum joined forces to publicize the plantation's plight, and their mutually respectful, sometimes jocular appearances on such national TV programs as the "Today" show got the word out.
The National Trust for Historic Preservation named Sotterley one of America's 11 Most Endangered Historic Places in 1996. A History Channel documentary brought Sotterley more attention, as well as just enough grant money to keep it going.
Sotterley was named a National Historic Landmark in 2000; Briscoe died in 2014.
Sotterley has spent about $4 million on renovations, operations, research and new programming since 2009, Easterling says, but supporters need to raise at least that much again to keep it sustainable.
Pirtle says it's worth the effort for the opportunity Sotterley presents to keep visitors engaged in conversation about the nation's slaveholding past.
Friday's ceremonies, Pirtle says, will reflect how far the effort has come.
"The slave cabin was Agnes' big thing," she says. "I think she would be thrilled."