Once a Beacon for Sailors and Madmen, the Blackwell Light Now Illuminates the Past

Between the asylum, penitentiary, multiple hospitals, sprawling apartment complexes, and the soon-to-be-completed Cornell Tech campus, Roosevelt Island has a history of unique architecture. And one of the Island’s more storied structures also happens to be its smallest: the Lighthouse.

Situated at the northernmost tip of the Island, the Blackwell Island Light, as it’s officially known, was built in 1872 and kept in use until 1940. Although the landmarked structure stands dark today, it once served not only as a beacon to passing ships but also as a rich source of Island lore.


The Blackwell Island Light was commissioned in May 1872 after a City official determined that the New York City Lunatic Asylum, which stood where the Octagon is located today, and the northern end of the Island needed to be lit at night to aid mariners in navigating at night. It was completed in September the same year.

The supervising architect of the project was James Renwick, Jr., designer of Saint Patrick’s Cathedral as well as the Island’s own Workhouse, City Hospital, and Renwick Smallpox Hospital. But even more interesting is the story of who is said to have possibly built the structure: patients at the nearby Lunatic Asylum.

The Madman’s Light

According to local lore, a warden at the asylum reported in 1870 that a patient, believed to be John McCarthy, had built a seawall at the northern end of the Island because he feared a British invasion. The wardens allowed him to continue his efforts because the wall stabilized and ultimately reclaimed an area of unusable marshland.

When the City decided in 1872 that a lighthouse should be built on the spot, McCarthy was supposedly bribed with fake money to demolish the wall. This is where stories diverge: some say the Lighthouse was then built by McCarthy himself, while others credit fellow patient Thomas Maxey with building the Lighthouse. However, urban legend favors McCarthy; an inscription found near the Lighthouse (until it mysteriously disappeared in the 1960s) once read:

“This is the work

Was done by

John McCarthy

Who built the Light

House from the bottom to the

Top all ye who do pass by may

Pray for his soul when he dies.”

The original inscription that appears to credit McCarthy with the construction.

Although there is no existing documentation to either confirm or refute any of these claims, it’s unlikely that either man built the Lighthouse singlehandedly. Other asylum patients were most likely forced to aid in the construction.

The completed Lighthouse stands about 50 feet tall and is made of gray gneiss (a banded rock consisting of feldspar, quartz, and mica) that was quarried on the Island by convicts of the Island’s penitentiary. Photographs from the late 1800s, and a 1903 short film shot by Thomas Edison, show the original Lighthouse with a much taller, steeper, more conical cap than it currently has.

The original Lighthouse had a taller, more pointed top, as seen in this drawing.

Operation and Decommission

While in commission, the lighthouse was operated independently by the City, with optics provided by the U.S. Lighthouse Board. Although an 1883 annual report from the Lighthouse Board praised the operations of the Island’s lighthouse, it also advocated for the banning of private lights, because “the lights, not being properly kept, go out from time to time.” The report specifically cited the Blackwell Island Light as having “gone out a number of times recently, and so much to the inconvenience, if not danger, of mariners, that a complaint has been made.”

A more reliable electric light was erected on Hallet’s Point, just 2,300 feet northeast of the Blackwell Island Lighthouse, a mere decade after the Lighthouse’s construction. After complaints that the new electric light was so bright it blinded boat captains, it was replaced with a small lantern in 1886, and later replaced by a 15-foot wooden tower, known as Hallet’s Point Light, in 1889. Despite the addition of the electric tower, the Blackwell Island Lighthouse was kept in operation until 1940. (The light on Hallet’s Point is still maintained by the Coast Guard.)


After being decommissioned, the Lighthouse fell into a state of disrepair. A partial restoration was performed in the 1970s and a full restoration was completed in 1998. The Lighthouse is now listed on the National Register of Historic Places and is designated as a New York City Landmark.

Today, the Lighthouse is the focal point of Lighthouse Park, a peaceful patch of grass with barbeque grills and picnic tables, where visitors can enjoy unique views of northeastern Manhattan, the Gracie Mansion, and the East River.

In 2012, Hurricane Sandy completely flooded the area around the lighthouse, washing away the pedestrian footbridges leading to it. The Lighthouse itself remained intact, and the entire area was reopened to visitors in 2014.

But more restoration work still needs to be done.

According to Judith Berdy, president of the Roosevelt Island Historical Society, a structural evaluation five years ago revealed that the stonework at the top of the structure is in poor condition and the lantern portion needs to be replaced. “The whole top of the Lighthouse is in danger of falling over.” She says Island officials have been putting off the work because they may have to do other work in Lighthouse Park to prevent future flooding to Coler Hospital.

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