Step into the sanctuary of the African Meeting House and you will walk on the same ancient floorboards where Frederick Douglass, William Lloyd Garrison and other prominent abolitionists railed against slavery in the 19th century, and where free black men gathered to shape the famed 54th Massachusetts Civil War regiment.

Following a painstaking, $9 million restoration, the nation’s oldest black church building is set to reopen to the public early next month. Beverly Morgan-Welch, who has spent more than a decade spearheading the project, calls the three-story brick building the nation’s most important African American historic landmark.

“This space has the echo of so many of the greats of their time … who were trying to figure out a way to end slavery,” said Morgan-Welch, executive director of the Museum of African American History.

Built in 1806 at a cost of $7,700, the meeting house sits on a quiet side street in Boston’s upscale Beacon Hill neighborhood, in the shadow of the Massachusetts Statehouse and nestled among handsome brownstones and exclusive private residences.

Long before modern office towers would hold sway, the building could be seen all the way from the city’s bustling waterfront, a “beacon on a hill” for black people longing for freedom, Morgan-Welch said.

It was one among a series of firsts for Boston’s vibrant black community, which by that time had already formed the young nation’s first black masonic order, an African Benevolent Society and an African school. Though designed as a place for worship, education, social gatherings and cultural events — “The Marriage of Figaro” was once performed there — it secured a place in history by becoming a headquarters of sorts for America’s anti-slavery movement.

“They prayed, they sang, they had songs like ‘I’m an abolitionist’ put to the words of Auld Lang Syne,” said Morgan-Welch, who described congregants as coming from every walk of life, including business owners, craftsmen, servants and seafarers.

Garrison formed the New England Anti-Slavery Society in the basement of the building in 1832.

“We have met to-night in this obscure school-house; our numbers are few and our influence limited; but, mark my prediction, Faneuil Hall shall ere long echo with the principles we have set forth. We shall shake the nation by their mighty power,” Garrison said, according to the historical record. The words are among those inscribed on a granite plaque outside the building.

Faneuil Hall, a short stroll from the meeting house, played a key role in the buildup to the Revolutionary War.

Douglass, who escaped from slavery to become a leading abolitionist, made one of several visits to Boston on Dec. 3, 1860. Historical records reveal a gathering at which he encouraged participants to present ideas for “the best way of prosecuting the anti-slavery movement,” listing both war and peace as possible avenues.

As war approached, the sense of urgency within the meeting house heightened.

Rallies were held to urge blacks to sign up for the 54th and 55th black regiments that would go on to fight in the Civil War. Volunteers came not only from Boston but from places as far as Canada and Haiti, Morgan-Welch said.

“They are preparing for war, they are preparing for what they know will come, they are extremely well organized,” she said.

The story of the 54th regiment was chronicled in the film “Glory.”

The building faded in prominence after the Civil War and was sold in the late 19th century. It would spend the next seven decades of its existence as a Jewish synagogue before being purchased by the museum in 1972.

Though named a national historic landmark in 1974, it would not be until 2006 that full-scale restoration would begin. The goal was to restore the meeting house to as close to its mid-19th century character as physically possible. No detail was overlooked, down to the square-headed nails typical of the time to replicating the original paint.

“They had people come in and do microscopic analysis of the all the paint layers,” said Carl Jay, director of historic preservation for lead contractor Shawmut Design and Construction. The goal was to identify the original color and composition of the paint, a process he likened to looking at growth layers in a tree.

Engineers and architects also faced the challenge of operating in a confined space in the densely-populated residential area, he said. In addition to restoring the original structure, a new wing was constructed to house elevators and other modern amenities.

The original floorboards in the sanctuary date back even further than the 205-year-old building, having already been in use for 70 years at Boston’s Old West Church before being moved to the meeting house when the church was relocated. Jay attributes the durability of the floorboards to the density of the wood used during the period.

The sanctuary’s curved pews are recreations of the originals, based on sketches from the time but enlarged to accommodate average modern day heights and weights. No rendering could be found of the pulpit, so it replicates others from the time.

The restoration was boosted by $4.1 million in federal stimulus funds. Morgan-Welch said other funding came from a variety of sources, including the National Park Service, the Massachusetts Office of Travel and Tourism, the National Trust for Historic Preservation and private corporations.

Next month’s grand reopening will be the emotional culmination of years of effort by Morgan-Welch, who recounts bursting into tears the first time she viewed into the completely restored sanctuary.

“Frederick Douglass walked here,” she says, slowly and almost reverently. Seated in the balcony, reachable by the same spiral staircase that congregants would have climbed two centuries ago, she reflects on what she hopes visitors will take away from the building.

“I would like them to understand that black people in America by 1806 had built for themselves a mighty, elegant and embracing space in which to worship, to educate, and to end slavery,” she said. (AP)