I think the transmitter moved to the WTC about 1973. I remember a nightclub in that building called "Broadcasters Inn".
IIRC, going way back to the early to mid 60s the Broadcasters Inn was a restaurant where you could watch the the broadcasters run the radio station through a large glass window as you ate your dinner.
I also remember that picture of the LPs being, impressively, handled with white gloved hands by the studio technicians.
In the early 60s, WTFM did broadcast from the tower at that location, but before moving to the World Trade Center WTFM joined WPAT-FM in transmitting from the Chrysler Building for a number of years. I don't know when WTFM moved to the WTC, but WPAT was still using the Chrysler Building when I worked there in the late 70s. The WPAT chief engineer had some real concerns about multipath problems from one tower at the WTC and was willing to wait to be on the other. I think WTFM's directional antenna was on the South Tower, and most, or all, other stations used the main mast on the North Tower.
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One last remembrance on Greater Media and WQMR, New Brunswick. Early on, Greater Media may have just wanted to park the WQMR call letters. Reading the FM article David linked to, I was reminded that WQMR had been the call letters of an AM station in Silver Spring, MD that Greater Media owned. It was paired with otherwise Beautiful Music formatted WGAY-FM in DC, simulcasting part of the day, and then, I think, the AM became WGAY-AM and the WQMR call letters were moved to New Brunswick. That DC area AM is now WFED, which provides programming aimed at federal employees.