Julia Koch David Koch 740 Park Avenue

The esteemed Lenox Hill property known as New York City’s “richest building” just lost New York City’s richest woman.

Julia Koch, widow of billionaire David Koch, sold an 18-room spread at the famed 740 Park Avenue co-op for $45 million, according to public records.

The socialite heiress was reported in 2022 to be shopping the duplex home for as much as $60 million. Her late husband had bought into the building, long-considered one of the city’s most exclusive addresses, in 2004 when he paid $17 million for the home.

Corcoran’s Leighton Candler had the listing.

The Rosario Candela-designed building houses 31 units, many of which have been home to the country’s most influential and wealthy families. In addition to the Kochs, the elite complex has housed old money — John D. Rockefeller, Jr. and a young Jackie Kennedy Onassis — and new, like Blackstone Group’s Stephen Schwartzman and hedge funder Israel Englander, who set the record for a co-op sale price when he bought a duplex for $71.3 million in 2014.

But outgoing residents have had a harder time getting their dream price in recent years.

Former Treasury Secretary Steven Mnuchin found a buyer in 2021 for a 6,500-square-foot home at the property, but it took three years and a 20 percent price cut. Ex-Merrill Lynch CEO John Thain sold his co-op in 2023 for $28 million, roughly even what he paid for it in 2006, while developer William Zeckendorf sold his pad in 2019 for a small gain from his 2011 purchase.

The sale of Koch’s capacious spread is the latest in a flurry of real estate moves the socialite and philanthropist has made since her husband died in 2019.

In 2023, she sold an Upper East Side townhouse at East 76th Street for $41 million. The off-market deal came five years after she and her husband purchased it for $40.25 million from real estate magnate Joseph Chetrit.

The previous year, Koch bought two apartments from Microsoft co-founder Paul Allen on East 66th Street for $101 million. The units included a penthouse and full-floor unit, which Allen purchased for $25 million in 2011 and $13.5 million in 1996, respectively.

Elsewhere in New York state, Koch bought an eight-acre Southampton estate for $70 million in 2021.