A duplex that once belonged to the late philanthropist and civic activist Marian Sulzberger Heiskell, of the New York Times family, is on the market for $2.99 million.

Heiskell, whose husband Andrew Heiskell was chairman of Time Inc., died earlier this year at age 100.

She is credited with spearheading campaigns that restored the theaters along 42nd Street, and for spearheading the creation of urban recreation centers as part of the 1972 Gateway National Recreation Area — 26,000 acres of parkland with beaches and wildlife around the New York and New Jersey harbor.

The four-bedroom, five-bathroom home, at 870 United Nations Plaza, features window walls that showcase East River and city reviews. The co-op opens to an entry gallery and a large living room that features a woodburning fireplace.

There’s also a formal dining room, and a kitchen with a butler’s pantry and laundry.

A grand staircase, plus an interior elevator and a back staircase, lead to an upper level that features the private quarters, including a three-room master suite with a windowed dressing room, closets and a spa-like bathroom.

Sotheby’s broker Nikki Field has the listing.