Fireworks displays set the skies ablaze on Thursday night as New York City celebrated the July 4 holiday. And as New Yorkers slept, scores of sanitation workers toiled overnight to ensure the streets were clean in time for the Friday morning rush.

“The city looks like the event never happened, which is always a good thing,” said Jeff Pitts, the city’s chief of cleaning operations. “With one of the biggest parties, comes the biggest cleanup.”

While revelry during most holidays is generally contained to specific areas – such as the New Year’s Eve parties in Times Square – July 4 celebrations are a citywide affair. Sanitation workers combed the entire city for bottles, cans and other litter at the numerous rooftops and venues where people congregated for the fireworks. The holiday fireworks also filled the air with small particles that contributed to the city’s poor air quality on Thursday evening.

This year’s fireworks show took place on an area of the Hudson River spanning from 47th Street to Houston Street, and sanitation workers split into three separate groups for the cleanup effort.

It took around 100 sanitation workers roughly two to three hours to sweep through parts of the city, according to Pitt, and they were armed with 18 mechanical brooms, 12 reloader collection trucks and about 50 manual brooms, Pitts said.

Pitt said that without the sanitation department’s cleanup efforts, drivers and cyclists struggling to avoid the trash would have to contend with a number of safety hazards the following morning.

And while parades and celebrations happen throughout the year, the sanitation department already has its eye on the next big holiday: Halloween, which is expected to require a similarly gargantuan cleanup effort once the festivities are over.

“We’re like the silent heroes because no one really sees what we do,” Pitts said. “They party – which we want them to do, we want them to enjoy the night – they leave and we take care of the rest. And in a matter of hours? You’ll never even know that there was a party that took place.”