Post was the granddaughter-in-law of Emily Post, considered the country's foremost etiquette expert. In 1965, five years after the elder Post died, Elizabeth took the helm of the Emily Post Institute in Vermont.
To Elizabeth Post, known to family and friends as "Libby," good manners meant having a kind attitude toward everyone.
"Libby was very open-minded, fair and flexible," daughter-in-law Peggy Post said. "She was full of common sense and kindness. Not at all pretentious and not at all stuffy."
Born in Englewood, N.J., in 1920, Post married William Goadby Post in 1944. He was the only grandchild of Emily Post, who wrote the seminal book "Emily Post's Etiquette" in 1922.
Elizabeth Post became active in the family business in the 1960s, at a time when manners and social mores were becoming more relaxed.
"So much was changing," Peggy Post said. "Libby kept that core message of etiquette going. Those principles of being respectful and considerate are important."
Along with revising "Emily Post's Etiquette" five times, Post wrote several books of her own. Her wedding etiquette books were especially popular. She also wrote a column for Good Housekeeping magazine for 25 years.
About etiquette, Post maintained that it should not be something that is "restrictive or unpleasant."
"Etiquette is meant to smooth the path between people to better relationships," Elizabeth Post once said.
She retired from the Emily Post Institute in 1995.