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NEW YORK — The nation's birthday bash got underway Wednesday, but officials around the country have been prepping for weeks to protect people at public venues.

Security measures at hard-to-protect public celebrations have been highlighted by low-tech attacks in London, Berlin and Nice, France, over the past year, as well as at a suicide bombing outside an Ariana Grande concert in Manchester, England, in May.

In New York, nearly 120 trucks filled with sand walled off the streets where crowds were gathered for the Macy's 4th of July Fireworks Show.

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Authorities developed the practice of parking trucks along New York City parade routes and other public gatherings after the Bastille Day massacre in Nice — in which a rented truck rammed into pedestrians — in July 2016. In addition, police have warned vehicle rental companies to watch out for suspicious transactions.

"New York City is the number one terror target," New York police Commissioner James O'Neill told reporters Friday. "We'll be able to take care of the city."

On two legs & four, your NYPD will be ensuring a safe, fun night on #July4th in NYC. #NYPDprotecting pic.twitter.com/onn9GKIW1d — NYPD NEWS (@NYPDnews) July 4, 2017

In addition to the several thousand uniformed officers and officers in civilian clothes, police are using radiation devices, explosives-detecting dogs and aviation units to monitor rooftops and traffic, Carlos Gomez, the NYPD's chief of department, said Friday

New York City Mayor Bill De Blasio added: "That's what keeps us safe. Do not be alarmed by that. Our officers are there to protect you, and we believe in strength in numbers. You'll see that visibly on July 4th."

An estimated 100,000 spectators showed up on Boston's Charles River Esplanade on Monday night for the Boston Pops Fireworks Spectacular Rehearsal, with 500,000 people expected Tuesday to see headliners Brian Stokes Mitchell, Andy Grammer, Melissa Etheridge and Leslie Odom Jr. perform.

New high-flying drones were deployed over Boston to receive and broadcast events on the ground. The technology made its debut over the Boston Marathon, with the ability to zoom in on objects nearly a quarter-mile away.

Los Angeles police also revamped their security guidelines for a July Fourth fireworks show in the San Fernando Valley. The changes aim "to improve security for the event due to ongoing issues happening around the world ... whether terrorism, or lone wolf [acts], or just general safety," Sean Dinse, senior lead officer of the Topanga Division, said Monday from Warner Center Park, where preparations were underway.

"This is something that we probably should have done a long time ago," Dinse said.

While officials stress that there haven't been any credible threats around the country, a small town in North Carolina canceled its Fourth of July activities. Downtown Hamlet announced Monday that the cancellation was due to “heightened security concerns" following a homicide that could be tied to gang violence last week.

Thousands of firework shows are set to fire off Tuesday night, in what promises to be a massive and hopefully safe celebration.