A brick row house that is one of only two documented stops in New York City on the Underground Railroad has a new penthouse with oversized windows. Preservationists say the addition not only violates construction codes, it literally stands in the way of its rich history.

The building at 339 W. 29th Street, once owned by the abolitionists Abby Hopper and James Sloan Gibbons, was among 12 row houses designated by the city’s Landmarks Preservation Commission as a historic district in October 2009. That means no major exterior changes are allowed without approval.

The inside had long ago been turned into a 10-unit apartment building. The current owner, Tony Mamounas, bought the building in 2004 and began renovations a few years later. He has said that he had permission from the buildings department to construct the extra floor before the home was declared a landmark, and he sued the city to continue the work and allow for tenants to move inside.

Earlier this week, a Manhattan Supreme Court judge ruled Mamounas could not rent out apartments unless he gets approval from the Landmarks Preservation Commission for the addition. Elisabeth de Bourbon, a spokeswoman for the commission, said Mamounas must first apply for the addition and the commission will decide whether it’s consistent with the rest of the district.

The level stretch of four-story row houses on what was then called Lamartine Place served as an escape route for the Gibbons daughters during the violent Civil War draft riots 150 years ago. While the racist mob ransacked and set the brick home ablaze, the daughters — the only ones home at the time — clambered to the roof and over the homes to a carriage waiting below.

The story is part of the reason the stretch was designated a historic district.

“If this fifth story remains, it obliterates their escape route, and future generations cannot envision easily how that escape took place,” said Fern Luskin, a professor of architectural history at LaGuardia Community College. “It is the legacy of this very important family, such a prominent Quaker abolitionist family, well known for their views, and that is why this house was attacked.”

The Hopper-Gibbons house survived the riots, which occurred over four days during the summer of 1863 after Congress passed the nation’s first draft law. Protests erupted as it became clear that the wealthy could buy their way out with $300 and devolved quickly into racist attempts to harm blacks and those linked to them, or abolition, as pent-up aggression over the war and slavery spilled into the streets

“That’s the reason for this being a historic district — the continuous roof line,” said Quaker and preservationist Julie Finch. “It’s a controversial part of our history, but also an important part. The family showed great courage.”

If Mamounas does not get approval for the penthouse, he may have to take it down. Several calls to his lawyer were not returned.

Mamounas said he would appeal. The building now looks much different from the other homes on the street, with larger windows and a modern facade.

The house and a church in Brooklyn Heights are the only stops on the Underground Railroad that were documented through letters and papers, Luskin said, though historians say other spots existed throughout the city.

(AP)