The greenway began in 1993 under Mayor David N. Dinkins. Alicia Glen, the current deputy mayor for housing and economic development, who worked for Mr. Dinkins when he was the Manhattan borough president, recalled poring over maps of the city with him, working out how to create parkland from what was mostly overlooked industrial waterfront. “This is something that has been dreamed of and talked about for decades,” she said.

“Just think how cool it’s going to be when the single most important island, maybe on planet earth, when you can walk or bike all the way around it,” she said. “That is one for the ages. That’s really exciting work.”

The expansion of the path circumnavigating Manhattan is welcome news for many, including those who use it for exercise.

“The more places and spaces for New Yorkers to run, the better,” said Chris Weiller, a spokesman for New York Road Runners. “Runners are always looking for new routes to run, and now if there’s a new loop around Manhattan, they can check one more thing off the bucket list.”