Departed icon: This 2016 photo offers a glimpse of the Watchtower sign, which stood atop the former headquarters of the Jehovah's Witnesses. Eagle file photo by Lore Croghan

The famous Watchtower sign was illegal for its entire half-century existence.

The Squibb sign that originally stood in its place was illegal, too.

That’s the city Buildings Department’s stunning assertion — and its rationale for why it denied the owner of the former Jehovah’s Witnesses’ headquarters in Brooklyn Heights permission to replace the Watchtower sign atop 30 Columbia Heights.

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The property’s owner, Columbia Heights Associates, is appealing the city agency’s decision.

Lawyers for the landlord and the Buildings Department duked it out at a city Board of Standards and Appeals hearing Tuesday night at Spector Hall in Lower Manhattan.

As a consequence of this legal battle, the void in Brooklyn’s shoreline scenery that was created by the Watchtower sign’s removal will remain for at least three more months. The next Board of Standards and Appeals hearing concerning this issue won’t take place until Oct. 23.

‘Iconic presence on the Brooklyn skyline’

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The red electric Watchtower sign had been “an iconic presence on the Brooklyn skyline,” attorney David Karnovsky of Fried, Frank, Harris, Shriver & Jacobson LLP said during his testimony on behalf of Columbia Heights Associates.

Workers removed the iconic Watchtower sign’s 15-foot-tall letters in December and left standing a flashing electric sign that shows the time and temperature.

The Watchtower sign had been visible from Brooklyn Bridge Park, the Brooklyn Bridge and Lower Manhattan.

The Jehovah’s Witnesses installed it in 1970, the year after buying 25-30 Columbia Heights from E.R. Squibb & Sons.

The Watchtower sign replaced a Squibb sign the pharmaceutical company had installed in 1961.

Did Squibb get a permit to install its sign?

The key argument by Timothy McKernan, the Buildings Department’s assistant general counsel, is that there’s no evidence Squibb obtained a permit to install its rooftop sign.

To counter that argument, Karnovsky testified that the agency acknowledges the availability of old Buildings Department records is limited.

Nevertheless, his team managed to find a 1961 Buildings Department ledger with a notation about an application to put a roof sign on top of 30 Columbia Heights. The estimated cost of erecting the sign was $20,000.

A Buildings Department employee’s signature of approval appears in the ledger notation.

Karnovsky’s team also found other documentation suggesting Squibb got a permit for sign construction.

Concerning the current situation with the iconic Watchtower sign, McKernan said in his testimony that putting new sign letters on framework that was left atop 30 Columbia Heights would constitute a structural alteration — and that’s not permissible, he asserted.

Karnovsky countered that an engineer’s study determined the framework is “a complete and viable structure” and the sign letters are not structural elements.

Jehovah’s Witnesses moved upstate after headquarters sale

Columbia Heights Associates bought the five-building Watchtower headquarters complex for $340 million in 2016.

The Jehovah’s Witnesses sold 25-30 Columbia Heights because they relocated their world headquarters to upstate Warwick, New York.

Columbia Heights Associates is redeveloping the property, which is across the street from Brooklyn Bridge Park, into an office and retail complex called Panorama.

Columbia Heights Associates is a joint venture made up of CIM Group and LIVWRK Holdings. Kushner Cos. initially was part of the joint venture but sold its stake in the property to CIM Group this year.

Jared Kushner headed Kushner Cos. until he stepped aside to serve as senior adviser to his father-in-law, President Donald Trump.