New York, New York - NYC Mayor-elect Eric Adams has selected a Long Island police chief to become the first female commissioner of the NYPD – opting for a backyard pick after an extensive national search for his first top cop, four sources told the Daily News late Tuesday.

Keechant Sewell, the chief of detectives for the Nassau County Police Department, was picked for the top NYPD post after doing a "fantastic" job in interviews with Adams and his team, said a police source familiar with the matter.

"She was out of this world good. They couldn’t believe how well she interviewed," the source said.

Adams, who will formally name Sewell as his commissioner during a press conference in Queens on Wednesday morning, heaped praise on the 49-year-old Long Island cop, who is set to become the first female commissioner in the department’s 176-year history once she takes over early next year.

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"Keechant Sewell is a proven crime fighter with the experience and emotional intelligence to deliver both the safety New Yorkers need and the justice they deserve," Adams said in a statement. "Chief Sewell will wake up every day laser-focused on keeping New Yorkers safe and improving our city, and I am thrilled to have her at the helm of the NYPD."

The selection of Sewell came after Adams and his team conducted a months-long search for the next commissioner.

Among those under consideration were Seattle Police Chief Carmen Best and Philadelphia Chief Danielle Outlaw. Juanita Holmes, the NYPD’s current chief of patrol, was also in the mix.

Adams, a retired NYPD captain, made a point on the campaign trail to promise to be the first mayor in city history to have a woman in charge of New York’s Finest.

In her Nassau County job, Sewell oversees just 351 law enforcement officers.

By contrast, as NYPD commissioner, she will oversee more than 35,000 cops in uniforms. She will also likely play a key role in realizing Adams’ vow to beef up the NYPD, including by reinstating the department’s controversial plainclothes anti-crime units.

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The Sewell pick received early backing from the head of the NYPD’s largest union, who has for years railed against Mayor de Blasio’s policing policies.

"We welcome Chief Sewell to the second-toughest policing job in America," said Pat Lynch, president of the Patrolmen’s Benevolent Association.

"The toughest, of course, is being an NYPD cop on the street. New York City police officers have passed our breaking point. We need to fix that break in order to get our police department and our city back on course. We look forward to working with her to accomplish that goal," Lynch added.