Post's daughter-in-law, Peggy Post, says the the 89-year-old died on Saturday in Naples, Fla.
Elizabeth Post became the spokeswoman for the Emily Post Institute in 1965 and for decades, wrote a column on manners and etiquette for Good Housekeeping magazine.
She was the granddaughter-in-law of the country's foremost etiquette expert, Emily Post.
Elizabeth Post revised the manual "Emily Post's Etiquette" five times, helping keep it current as social norms have changed since its original printing in 1922.
