Nassau County officials thanked on Monday a gravely ill retired FDNY firefighter from Hicksville — who successfully pushed Congress to continue funding health care for sick 9/11 first responders — by giving him a key to the county.

Ray Pfeifer, a 27-year FDNY veteran who is battling stage 4 cancer attributed to his work at Ground Zero after the terrorist attacks, made more than a dozen trips to the capital to convince hesitant lawmakers to pass the James L. Zadroga 9/11 Health & Compensation Act.

“We’re dying from the terrorists — 14 years later — we still are,” said Pfeifer, who received a standing ovation from members of the public packed inside the Legislature’s chambers in Mineola. “All I did was go down and fight the politicians who wanted to fight us.”

Mangano presented Pfeifer, who was accompanied by his wife, Caryn Pfeifer, and father-in-law, Richard Baldassano, with the key to the county in a private ceremony in his office conference room, before he was publicly recognized by Legis. Rose Walker (R-Hicksville).

Mangano cited Pfeifer’s “heroism and determination” in fighting for the legislation’s extension, despite his own health battle, which includes chemotherapy and radiation for a brain tumor and the loss of a kidney. Pfeifer also had his leg rebuilt and walks with the help of leg braces.

“Ray’s tireless service and dedication, reminds us all to never forget the sacrifices made by the men and women who served at ground zero and continue to lose their lives,” Mangano said in a statement.

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Congress voted last month to extend the Zadroga Act, named in honor of an NYPD officer who died of respiratory disease. Some lawmakers had argued against the extension, pointing to what they said was a lack of scientific proof that the reported illnesses were directly related to 9/11.

“It just proved to the country — never forget. And we held them to it,” said Pfeifer, 57, who was assigned to Engine Company 30 on the Upper West Side. “It should have never been a problem. It should have been done right away. ”

Walker, a personal friend to Pfeifer and his family — which includes his son Terence Pfeifer, 23, an FDNY EMT — joked to Pfeifer that her citation was smaller than Mangano’s and she didn’t have a key to give him, but “there’s a lot of love packed in this citation.”

A humble Pfeifer, who received the key to the city from New York City Mayor Bill de Blasio earlier this month, downplayed his individual role — saying many survivors lobbied — but acknowledged there was something special about being honored in his own community.

“I love this county,” said Pfeifer. “I love where I grew up in Levittown. I live in Hicksville now. There’s nothing like Nassau County, believe me. Thank you so much. It’s way over the top for one guy who’s just the poster boy.”