Emily Post, who died in 1960, spent much of her life updating her 1922 book on etiquette, and writing about it in newspaper columns.

KRT / FILE PHOTO

Here are facts about Emily Post you never would’ve suspected: She played the banjo. She wore red shoes. She helped bring children orphaned from the Holocaust to America.

And, probably most shocking, she occasionally rested her elbows on the table.

Laura Claridge’s Emily Post: Daughter of the Gilded Age, Mistress of American Manners (Random House; 445 words; $30) skewers all the clichés and caricatures you might have had about the grande dame of etiquette. The biography spans the Victorian Era, the Great Depression, two world wars and continues through Post’s death in 1960.

Claridge, who lives in Saugerties, N.Y., was joking with her husband about how she used to prop Etiquette, Post’s veritable Bible of social manners, on her head to improve her posture, and she began thinking about its author.

When she looked for a biography, she was surprised there wasn’t one. Claridge, the biographer of Norman Rockwell and Tamara De Lempicka, thought: “Here’s my project.”

Post’s family was more than willing to cooperate, but many of Post’s personal records had been destroyed. Relying on newspaper clippings, letters to agents and other sources, Claridge began piecing together the life of Emily Post.

“She really was a doer,” Claridge said in a recent phone interview from San Francisco while on her book tour. “When life got her down, she would pick herself up and go ahead and greet the next day.

“Her mother was smashed into a tree and killed [in a car crash],” Claridge said. “Her beloved father died of stomach cancer, and then before all that — a horribly humbling and humiliating divorce. In each instance, she picked herself up and went ahead and did what she had to do.”

Post’s fortitude proved an inspiration for the biographer. As Claridge immersed herself in the project, she felt her interest waning, which wasn’t normal. The reason for the change in her behavior was a lethal form of brain cancer that nearly killed Claridge. When she began recovering, she couldn’t even recall Post. A doctor told her she would never write again.

“It was like the ghost of Emily inspiring me,” Claridge said. “Nothing will motivate someone more than being told that they can’t do it, right?”

While she lost about a year of work, she eventually found herself back on the project.

“So finally when I understood who Emily Post was and I was writing a book on her, I got sort of excited — especially after the doctor commented that I’d never write again. I was full of energy,” Claridge said. “Now I was all motivated. I couldn’t wait. When I got home, I sat down at the computer and I really wrote better than I ever have.”

Claridge documents Post’s life from a young girl who idolized her architect father (Bruce Price, the designer of Tuxedo Park, N.Y.) to her rise as the country’s foremost authority on etiquette.

Post became a prolific writer, publishing articles and serialized romantic stories in magazines and novels. Eventually, she would be persuaded to write about etiquette, publishing the seminal Etiquette: The Blue Book of Social Usage in 1922.

Emily’s panoramic vision of her subject contained advice that today would come from a marriage counselor, psychologist, doctor or fashion consultant, Claridge wrote.

Etiquette took off. Post spent much of the rest of her life updating it and answering questions in newspaper columns and radio shows.

“One of the main themes of Etiquette is to show people — all people — respect,” Claridge said. Post was known to treat her servants exceptionally well, which in turn brought her loyalty and friendship. Post also urged readers to never embarrass others who committed a social faux pas.

“Emily was deeply offended by the pretentious and the pompous, and she disparaged especially the supposed ‘omniscience of the very rich.’ ”

Claridge unearthed more surprises about Post that even her family didn’t know. After hearing that Post had helped bring orphaned Jewish children to America, Claridge was dubious. Then she carefully listened to tapes made during Steven Spielberg’s Holocaust project in which one of the orphans, Isaac Hass, spoke about Post’s involvement in helping him leave Germany.

Post’s grace lives on. Her descendants maintain the Emily Post Institute and continue writing books on manners, which include an updated Etiquette, children’s books and the new Do I Have to Wear White? by Anna Post.

“I kept being struck by how she almost seemed a precursor [to] Oprah Winfrey or Martha Stewart, and that she ended up commanding an empire,” Claridge said.