In July 1995, the artist Maura Sheehan installed a skateable sculpture in the anchorage of the Brooklyn Bridge, over on the Brooklyn side. Ms. Sheehan became fascinated with skateboarders after observing large groups of them careening through the streets downtown in the era before 9/11.

Much of that part of the city was still accessible to herds of rule-bending youth. “Their building of community is really a profound thing,” she said of the eclectic groups of skaters she would encounter. “It forces discourse and interaction.”

The hidden work — a halfpipe that she found through a group of “cowboy” skaters traveling cross-country from California, who reconstructed it in every city they stopped in — attracted more than just skaters. Ms. Sheehan recalled daredevils and spectators alike being drawn to the structure. “It really was a living social organism,” she said.

Steve Rodriguez, 46, a professional skateboarder and the owner of 5boro skateboards, helped build Ms. Sheehan’s ramp in 1995. A little more than a decade later, on the Manhattan side of the bridge, he helped organize the city’s skate community in order to save a portion of the so-called Brooklyn Banks, a popular spot for local skaters at the time. In this case, the city promised to eventually turn part of the area into a proper skatepark.