Thousands of people representing different backgrounds, faiths and traditions across Long Island marked the 15th anniversary of the 9/11 terrorist attacks with calls for healing and unity.

On that day 15 years ago, many Americans awoke to incredible images on their TV screens, then fumbled for their phones, dialing furiously, trying to learn if their loved ones were among those at the epicenter of an attack.

On Sunday, in their own ways, Long Islanders grieved the nearly 3,000 lives taken on Sept. 11, 2001, at the World Trade Center, the Pentagon and on an airliner that crashed in Shanksville, Pennsylvania.

Many called for Americans to continue to teach the lessons of that day to generations that didn’t live through it, or who weren’t old enough to feel the profound sense of “before and after,” as 9/11 has become an unforgettable bookmark in history.

“This is a day that must always be remembered, it can’t leave our memories,” North Hempstead Supervisor Judi Bosworth said at a memorial service in Manhasset that drew more than 100 people, including elected officials, veterans, choir singers and Boy Scouts.

“This is our future generation,” Bosworth said of the Boy Scouts. “These are the young people who are going to provide the leadership to make sure 9/11 is always remembered with the respect it needs to be, and that those whose lives were lost will always be in our hearts.”

Officials at the ceremony read the names of the 56 North Hempstead residents who died in the towers. After each name was read, a bell was struck. Three rifle shots rang out in salute and taps was played on a trumpet.

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“It’s a reminder that we are not only a family of Americans and New Yorkers, but we are a family of Long Islanders as well,” said Assemb. Charles Lavine(D-Glen Cove). “This is what family does for family.”

State Sen. Jack Martins said the ceremony was a “reaffirmation of our commitment to never forget.”

“It’s extraordinarily important that we continue these traditions, mourn loved ones lost, and celebrate the hope of a better future,” said Martins (R-Old Westbury).

That sentiment was evident in Point Lookout Park in Hempstead, as thousands solemnly gathered under cloudy skies to honor the nearly 500 Long Islanders who died in the attacks.

Among them was Jeffrey Morgenstern, whose sister, Nancy Morgenstern, 32, a Cantor Fitzgerald employee, died in the attacks.

“It’s hard to believe I haven’t seen her in 15 years,” the Woodmere resident said.

At Point Lookout, some cast carnations in a reflecting pool and wrote the names of victims on a 35-foot-long remembrance mural. Miniature American flags were placed around the base of a 9/11 sand monument on the beach.

Kerri Kiefer-Viverito remembered her brother, Michael Kiefer, 25. The FDNY firefighter from Franklin Square died rescuing people from the towers. While he has missed many milestones, Kiefer-Viverito said her brother always will be part of the family.

“Michael, we miss you more and more with every second,” she said at the Point Lookout ceremony. “We love you with all of our broken hearts.”

At Farmingdale United Methodist Church on Main Street, congregants remembered 9/11 with a special service as part of their regular service.

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The program included prayers for those who lost their lives on that day. FDNY firefighter Christopher Sullivan of North Massapequa was remembered as a man of faith who put public duty first.

Elsewhere on Long Island, people found different ways to reflect on the anniversary.

Holly McGregor, a teacher at Dipamkara Center, a Buddhist meditation center in Huntington, led more than 80 people in an ancient Tibetan meditation of love and compassion, and a silent walk of remembrance Sunday morning at Heckscher Park in Huntington. The session, like many on Long Island, included a moment of silence at 8:46 a.m. and 9:03 a.m. to mark the moment when each tower was hit.

“Nine-eleven was a deep, shared experience for all of us, although tragic and heartbreaking,” McGregor said.

Army veteran Jonathan Cammarato, 28, said it felt right to come to the meditation in Huntington.

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“It felt like it was my duty,” he said. “It’s important to know that love is there.”

In Westbury, about 60 people came together at the Islamic Center of Long Island to dedicate a plaque honoring the victims of 9/11.

The green and gold plaque, made of brass and set in stone, bore an inscription from the Quran: “To Allah we belong, and to Him is our return.”

Isma Chaudhry, president of the Islamic Center, said before the veil was removed from the plaque that she hoped “we take off those veils of bigotry and hatred as well.”

“We lost these beautiful people, individually and collectively,” Chaudhry said. “However, we have to understand that we have to heal as one community.”

That ethos, she said in an interview after the 40-minute ceremony, is “the only way we’ll let these extremists down.”

Some at the service reflected on the toll the attacks took on their faith and the prejudices lodged at them over the years.

“Let’s try to take back our religion from the fundamentalists and terrorists,” said Qamar Zaman, chairman of the Islamic center’s board of trustees.

Westbury Mayor Peter Cavallaro said the ceremony “dispels all those myths and all those things that people believe about the Islamic community, and Muslim community, that just aren’t true.”