One of the only surviving photographs we have of Lillie Bliss—fashionable in a fur-collared coat and a satin hat with a flourish of feathers—is by all accounts misleading. This elegant ensemble was likely one of only two owned by Miss Bliss, who despite her great wealth was a modest, intensely private spinster. Lively, wide-open eyes and a Mona Lisa smile hint at what friends described as her “radiant spirit.” A co-founder of the Museum of Modern Art, Miss Bliss was also a stealth rebel.

It was she who foresaw the need for a new kind of museum in New York City, she who conspired with a small circle of like-minded devotees and put her collection on the line to make it happen. “Lillie P. Bliss and the Birth of the Modern,” an exhibition that opens on November 17 at the Museum of Modern Art, showcases the unassuming pioneer.