Leonard Stern inherited leadership of his father's Hartz pet-products business, expanded it substantially, then redeployed proceeds from its sale into a large private real-estate and investment group. [1][2]
He inherited an operating business and materially expanded it
Forbes' historical billionaire coverage says Leonard Stern took over his father's Hartz Mountain Pet Products business, making an established family company the starting point for his wealth. [1]
NYU Stern says his father Max arrived in the United States with little beyond a shipment of canaries, gradually built a pet-supply business, and handed control to Leonard in 1959. [2]
NYU Stern credits Leonard with building that inherited business into a giant pet-food and pet-supply company before the family sold the pet-products operation in 2000. [2][1]
He transformed the family enterprise into a major real-estate platform
Forbes reported that Stern reinvested proceeds from the pet-products sale into a large commercial real-estate portfolio in New York and New Jersey. [1]
NYU Stern currently identifies him as chairman and chief executive of The Hartz Group, one of America's largest private owners of commercial real estate, supporting material expansion beyond the business he originally inherited. [2]
Sources for background
Sources reviewed Sep 23, 2026.
- Leonard Stern · Forbes · Mar 8, 2007
- 100 Million Reasons to Believe · NYU Stern
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