Welcome back to Camera Obscura, Curbed's series of photo essays by Nathan Kensinger. This week, Kensinger explores NYC's abandoned landmarks.

In the 50 years since New York City's Landmarks Law was passed, over 1,300 individual landmarks and 109 historic districts have been designated by the Landmarks Preservation Commission, amassing an impressive array of protected properties and neighborhoods throughout the five boroughs. The landmarking process, however, does not guarantee a permanent safe harbor for buildings, and over the years many designees have been lost to decay, demolition, and legal maneuvering. Today, a surprising number of official New York City landmarks are abandoned, having been left to rot for decades, and are in danger of becoming victims of demolition by neglect.

These abandoned landmarks range in size from humble structures like the 17th century Abraham Manee House, designated in 1984 and now deteriorating in an overgrown field, to the New York City Farm Colony/Seaview Hospital Historic District, a sprawling campus with dozens of empty, collapsing buildings, which was designated a landmark district in 1985 and then left to the elements. Both of these examples are located in Staten Island, but abandoned landmarks can be found in every borough. Most are monumental civic structures, including schools, courthouses, and hospital buildings, and in recent months, several of these institutional ruins have been in the news, as the latest wave of development sweeping through the city has plucked them out of obscurity, pushing them toward either demolition or redevelopment.

"Many of these standout historic buildings that have been neglected for years and years are publicly owned, in one form or another," said Simeon Bankoff, the Executive Director of the Historic Districts Council, an organization that advocates for historic neighborhoods. "What happens is that the government—city and state—generally does not have the will or the money to develop, much less maintain, historic properties…and with the economic downturn, everything just stopped. Private money was not wanting to take a risk on these long term projects." As the economy has rebounded over the last few years, developers and city agencies have shown an increased willingness to take on large-scale redevelopment projects. "So now these plans are wending their way through, there is enough money back in the system to get things going again, and it's all kind of hitting during the building cycle this year."

The list of abandoned NYC landmarks which are now undergoing transition include the Bronx's long-empty P.S. 31, which was designated a landmark in 1986 and is currently being demolished, and the Old Bronx Borough Courthouse, landmarked in 1981, which reopened its doors to the community for the first time in 35 years this April. In Brooklyn, renovations are underway at the decrepit Coignet Stone building in Gowanus, the remains of the Domino Sugar Refinery in Wiliamsburg, and the shuttered Empire Stores and roofless Tobacco Warehouse in Dumbo's Fulton Ferry Historic District. In Queens, the crumbling New York State Pavilion, designated in 2009, may soon get a paint job and $5.8 million in repairs, while in Manhattan, city agencies are now seeking to tear down the unused 1907 Tin Building, which is part of the South Street Seaport Historic District. And later this summer, the High Bridge, which was designated a landmark in 1970, is scheduled to reopen after being closed to the public for decades and undergoing a multi-year renovation.

"Certainly, some of these sites that have lingered for a few years or longer are being swept up in the development boom," said Andrea Goldwyn, the Director of Public Policy at The New York Landmarks Conservancy, which maintains a list ranking New York City's abandoned historic buildings by their degree of decay. "A number of them are unfortunately now in worse condition, or are gone. But some are in better shape," said Goldwyn. "The institutional ones are the ones that still are yet to be resolved. Maybe the economic boom is finally carrying those along."

Despite the efforts of advocacy groups like the Landmarks Conservancy and the Historic District Council, the decision of whether New York's abandoned landmarks are either restored or left fallow is often determined by private investment and the vagaries of an unreliable economic system, and not by their historic value or support from government agencies. While landmarking a building may provide some measure of legal protection, without significant public investment, many historic civic buildings will remain endangered. "When cities actually invest in rehabbing," said Bankoff, "if you actually just suck it up, and put the money into the buildings, they will, if you look at it from a 20 year perspective, be a real catalyst for growth… Because it doesn't do anybody any good just sitting there rotting. I mean, that really tells the wrong story."

P.S. 31 in the Bronx is currently being demolished. The school, which is owned by the Department of Citywide Services, was closed down in 1997 and left to decay. "P.S. 31 makes me want to curse in Yiddish," said Simeon Bankoff. "Had that been a private owner, the city of New York would have sued the heck out of them, but because it's a city owned property…"

"I hate to see the building torn down. It has a long history," said a neighbor who attended elementary school here, when the building was known as The Castle on the Concourse. "They let it deteriorate beyond a certain point, so they didn't have to clean it up. Why can't they make it into a museum or something?"

The Old Bronx Borough Courthouse, which has been sealed up since 1978, is awaiting development by its owner. "That's another situation where it's a beautiful building, they just don't quite know what to do with it," said Bankoff. "Every time they delay doing it, it just goes up in price."

An art exhibit by No Longer Empty has opened the lower floors of the courthouse building to the public, but the upper floors remain unused, empty, raw spaces.

The fenced-off Kingsbridge Armory, landmarked in 1974, has been vacant since 1996, according to the NYCEDC. A private developer's plans to transform it into "the world's largest indoor ice facility" were announced in 2014, but delays were reported this April.

The stench of decomposition wafts out of the building's basement floors and into the neighborhood's streets. "It's been empty a few years," said one Bronx neighbor. "I took a peek inside once, through the front door. It's huge!"

The Andrew Freedman Home, on the Bronx's Grand Concourse, has been slowly recovering from decades of neglect. This 1924 building was landmarked in 1992. Its upper floors were once used by squatters and graffiti artists.

Originally designed as a home for "indigent capitalists," the building is now open to the public and hosts parties and events in the ballrooms on its ground floor. The upper floors, however, remain in ruinous condition.

The campus of the New York City Farm Colony, as it appeared in 2014. This Staten Island historic district is currently being transformed into a senior housing complex, after sitting abandoned for decades. "They are planning to demolish some of the buildings that can't be reused, and hopefully reuse some of the historic fabric," said Andrea Goldwyn. "Thats a pretty good resolution considering everything that has happened there."

"We saw the plans, they are pretty good. Not perfect, but pretty good," said Simeon Bankoff. However, across the street, on the grounds of the Seaview Hospital historic district, no plans have been announced to renovate the abandoned sections. "They've just got big old rotting buildings everywhere."

In Brooklyn, the abandoned 18th Precinct Stationhouse and Stable, later renamed the 68th Police Precinct, was recently offered up for sale by its owners, a local community group. The asking price for this Landmark was $6 million.

The precinct's interior, as seen in 2011, is a hollowed out shell. Floors and walls have collapsed into the cellar. "The people who were running it were great people who have a solid history in the community. But they didn't have the financing," said Bankoff, "and they just let it sort of fall apart around them."

The Coignet Stone building, as seen in 2008, was designated as a Landmark in 2006. Left empty by its owner for many years, it was taken over by squatters soon after its designation. The building's long history was explored in the 2013 documentary "At the Corner of 3rd and 3rd" by Max Kutner.

Today, this 1872 structure is being renovated by the surrounding Whole Foods Market, which has transformed this once quiet corner into one of the busiest intersections in the Gowanus neighborhood.

In Dumbo's Fulton Ferry Historic District, the Empire Stores warehouses are undergoing a massive renovation. After being unused for six decades, the structures will become office and retail space.

The once-roofless Tobacco Warehouse will soon reopen as the new home of St. Ann's Warehouse. After being left exposed to the elements for over 40 years, the structure will become a theater with room for up to 700 people.

Only one structure remains standing at the Domino Sugar Refinery in Williamsburg, Brooklyn, housing the refinery's filter house, pan house and finishing house, which were landmarked in 2006. The majority of this historic complex, unused for several years, has since been demolished.

As the renovation the refinery buildings continues, the rubble of destruction is slowly being cleared away, to make way for a new residential development built by the Two Trees Management Company.

"I think we are fortunate that some of our Landmarks, our historic buildings, are so well built, so well constructed, that even if they are not used right away, they can weather some of these storms," said Andrea Goldwyn. "Sometimes you have to wait for the right situation to come along."

Further north on the East River, the stabilized ruins of the Renwick Smallpox Hospital on Roosevelt Island are a reminder of the durability of these older structures. Currently undergoing a $4.5 million renovation, this is one of the only ruins to be designated as a New York City Landmark, though many other buildings have fallen into a ruinous state after being landmarked.

· Nathan Kensinger [Official]

· Landmarks at 50 coverage [Curbed]

· Camera Obscura archive [Curbed]