On April 24, New York City Mayor Michael Bloomberg released a digital trove of 870,000 photographs, maps and videos that document more than 150 years of Big Apple history, starting in 1858. Among the highlights is a series of images showcasing the construction of the Brooklyn Bridge, which opened to the public 129 years ago on Thursday.

The evocative, black-and-white photographs are not only remarkable for the intimate and playful details they capture, including a shot of workers painting the Brooklyn Bridge in 1914—without harness!—but also because they were taken by an amateur photographer named Eugene de Salignac, who was a municipal worker from 1906-1934.

Eugene de Salignac

Under the bridge on the Brooklyn side, 1918.

“He was an extremely talented photographer who was tasked with documenting the building of the city,” says Eileen Flannelly, New York City’s deputy commissioner for the department of records. “Unfortunately, he didn’t get recognition for his images during his lifetime. He was just a civil service employee, really unknown. I don’t think people really understood then that he was showing us how our city was built.”

The push to unveil this digital archive has been in the works for nearly four years, and it’s likely to become a hallmark achievement for Mayor Bloomberg, who has made it a mission to support technological initiatives during his tenure. Other photographs from the archive give viewers an inside look at the city’s grisly crime scenes, old Times Square and various borough presidents’ offices. “I look at the crime scene and it’s like looking at an old gangster movies—they’re fascinating because they don’t look real,” Flannelly says. “Then I look at pictures from the ‘80s and see how much the city has changed. It’s fascinating because you don’t have to go too far back to see how far we’ve come.”

The New York City Municipal Archives Photo Gallery can be browsed online here.