Pete Alonso is a born-again New Yorker.

A Tampa, Florida, native, Alonso became a face of the Mets during his historic rookie season. He plans to live in his Upper East Side apartment for parts of the offseason. He orchestrated the Mets’ 9/11 tribute last month — buying specially made commemorative cleats for all of his teammates, who wore them during a game — and he has spoken often of the way the fan base and city have made him feel welcome.

“New York has embraced me,” Alonso said recently. “I’m just so thankful. I want to keep saying thank you to everybody in the city. Mets fans especially. This is home. This is home now."

That made Alonso’s appearance Tuesday in downtown Manhattan all the more meaningful — and obvious — for him. He donated his 9/11 cleats, as well as a bat, to the 9/11 Memorial & Museum, adding to what he called an “absolutely breathtaking” collection of artifacts.

“The fact that you guys are willing to have me just donate a stinky old pair of cleats is, really, to me, so humbling,” Alonso said of his size-13 Nikes.

On Sept. 11, the 18th anniversary of the terrorist attacks, Alonso and his teammates wore the red, white and blue cleats. The shoes depicted images of the American flag, plus the Sept. 11, 2001, date, “We will never forget” and lettering for the first-responder agencies involved.

Initially, Alonso said, he asked Major League Baseball if the Mets could wear first-responder caps, which they traditionally wear for pregame activity, during the game. When MLB said no, Alonso opted to go the footwear route, asking for forgiveness instead of permission. The cleats were covertly delivered to Citi Field that afternoon to minimize the chance anybody could tell the Mets no.

“I don’t know why there is red tape, but it’s unfortunate,” Alonso said. “We found a way around it, so if we can’t make something [with the hats] happen, it’ll be a yearly thing, we’ll wear the commemorative cleats.”

The Mets scored nine runs on 11 hits in a win over the Diamondbacks that night.

“You can’t tell me there’s no magic in baseball,” Alice M. Greenwald, the museum president, said. “And you [Alonso] have been part of that magic this season.”

After seeing the Mets’ tribute, the museum reached out to Mets chief operating officer Jeff Wilpon, who passed along the donation inquiry to Alonso.

“I barely got the words out of my mouth that the museum wanted them before Pete said, 'Absolutely,' " Wilpon said.

Consider it another stage of Alonso’s evolution into a New Yorker.

He was 6 years old on Sept. 11, 2001. He said that although he always sort of understood what happened, he didn’t fully grasp it until 2016, when he spent his first professional season playing in Brooklyn for the Mets’ short-season Class A team, the Cyclones. He remembers seeing commercials about how those who were at the pile of debris at Ground Zero are entitled to compensation for resulting injuries and/or illness.

“It’s like, wow, this is something that is not just one specific day. It’s lingering,” Alonso said. “That’s when I really understood, really started to grasp it. It’s still a tremendous day that I don’t think I’ll ever fully understand. But I want to understand as much as possible and give all I can to help.

“I try to not just be a good ballplayer, but I want to be a good person as well. I feel like I have such a really cool platform, and I don’t want to just play baseball and be good at it. Hopefully, I can impact other people’s lives and make someone else’s life better. I just want to do good.”