It is easy to forget what Central Park looked like in the 1980s. But Douglas Blonsky, president of the Central Park Conservancy, can see past the lush meadows and fresh streams to a time when the 843-acre park was more beaten-down wasteland than urban Eden.

Gazing at the Great Hill, an emerald lawn flecked with boulders at the park’s north end, Mr. Blonsky, 58, remembered what it was like trekking there to discuss its restoration.

“There were mattresses all over the place for prostitution and drugs,” he said. “And we would be sitting here trying to do this work, and everybody would just be staring at you. Now, it’s baby carriages and dogs and picnics.”

As Mr. Blonsky announces his retirement on Tuesday from the conservancy, a nonprofit group founded 37 years ago to rescue Central Park from decades of neglect, his imprint on the park’s landscape is everywhere.