There’s a dark, windowless room in the Manhattan Borough President’s office where centuries of New York City history live.

That room is where Hector Rivera oversees hundreds of years’ worth of maps — historical and modern — as the borough’s official topographer. He serves as a liaison between the borough president’s office and city agencies as well as businesses. He assigns addresses for new buildings, maintains street information and knows what lies beneath Manhattan’s buildings, basements and tunnels – and he’s been learning about it for three decades.

“When I first got there, there was no internet," he told Gothamist. "There was a dial-up and there was no network. We had the dot matrix printers."

Rivera became Manhattan’s map guy by accident. He started as an intern in 1994 under Borough President Ruth Messinger, making photocopies of speeches and agendas.

In 2008, when then-Borough President Scott Stringer asked Rivera to move over to the map room because of his talents for organization and computer technology, not much had changed. Rivera said there was no technology in the map room at all.

He had one task: upgrade it. He was a man with a digital camera and a mission.

“I was just there to basically do a technical, take these old papers and convert them into a digital format to provide access to the people,” he said.

But as the years continued to go by, Rivera started thinking of himself as a historian rather than just a technician.

A neighborhood map from 1884 is among those overseen by Manhattan's topographer

The current borough president, Mark Levine, says Rivera keeps historical records of Manhattan going back to colonial times as part of his job.

“You can see underground streams on properties from the 1700s,” Levine said, which is the kind of information that could help city agencies solve modern day engineering problems.

While Rivera is usually a behind-the-scenes staffer, doing tasks like assigning new Manhattan buildings street addresses, one of his biggest responsibilities happens alongside Levine.

Together, they can officially remove streets from Manhattan’s street map, which they did together for the first time in May, as city officials prepare to replace the Port Authority Bus Terminal in Midtown.

Rivera and Levine cleared away a portion of West 41st Street near 8th Avenue from the official maps of the borough. The borough president’s office says taking this street off the map helps keep congestion and pollution out of Manhattan as well.

“If they're coming in from Jersey, and their one stop is the Port Authority Bus Terminal, they don't have to hit a Manhattan street-level street,” Rivera said. “They go through the tunnels and [will] have direct access to the new terminal.”

The practice is relatively uncommon; he said map changes may happen 4 times in a decade.

But, little by little, Rivera has watched the streetscape transform with each one.

“We're not erasing history, we're maintaining it,” he said