About 25 members of the Nassau County Police Department began a nearly 300-mile bicycle ride Monday to raise money and awareness for police officers killed in the line of duty.

Acting Nassau Police Commissioner Thomas Krumpter was among the Nassau riders when the annual Police Unity Tour pedaled off from the Sept. 11 memorial in Manhattan to the National Law Enforcement Officers Memorial and Museum in Washington, D.C.

After a ceremony at the Sept. 11 memorial’s reflecting pools, the Nassau contingent joined with other officers, including about 200 from the Port Authority, for the bike ride.

The charity bicycle ride, in its 19th year, will cover about 300 miles over four days. When it ends Thursday, thousands of police officers converge with the goal of raising money for the upkeep of the museum and memorial — a pair of curved marble walls with the inscription of the names of every law enforcement officer killed in the United States. Last year, the bike ride raised $2.1 million.

The families and friends of the fallen, just as they do every year, will line the streets in support, carrying signs and remembrances.

“It’s very, very emotional,” said Nassau Det. Sgt. Jo-Ann Distler, a 31-year department veteran in the district attorney’s squad who will bike the tour for the third time. “These are all families of law enforcement officers who have lost their lives and it really puts into perspective what we do. . . . We remember those that sacrifice their lives for what we do for a living.”

This year, the name of slain NYPD Officer Brian Moore, a Plainedge resident, will be added to the D.C. memorial.

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Five Nassau police officers have died in the line of duty since 2011 — and the Nassau contingent of the unity tour will have those fallen brothers in the forefront as they ride, said Nassau police Lt. Timothy Rooney, who is on the board of New York’s 37 Chapter, named for the number of Port Authority police officers killed on 9/11.

“It’s one of the few memorials that will never be finished,” Rooney said. “I’ve been there at different times throughout the years and you’d be surprised how many families of the fallen officers visit there. It’s a place of solace for them. . . . It means a lot to the families.”

Nationally, there have been 30 line-of-duty deaths this year through April 3, up from the 27 that occurred during the same period last year, according to statistics from the National Law Enforcement Officers Memorial Fund. Last year, 123 law enforcement officers died in the line of duty.

Krumpter’s bike-riding debut marks the first time that he, or any other Nassau commissioner, has participated in the tour.

“I always wanted to do the Unity Tour,” Krumpter said. “We in law enforcement always talk about never forgetting the fallen, people that made the ultimate sacrifice, and this bike rally truly demonstrates this. . . . I always wanted to do it and now I’m in the physical condition to attempt this bike ride.”

Krumpter lost 70 pounds during the past year by exercising and cutting back on junk food, he said.

The impetus for slimming down, the 49-year-old said: “Getting older; I wanna be a little more healthy.”