Mariclare Costello died on April 17, 2026, in Brooklyn, at the age of 90  — and the world that loved her as the warm, quietly radiant schoolteacher Rosemary Hunter Fordwick on The Waltons is only now learning the full picture of a life so rich, so layered, and so genuinely extraordinary that the single role most audiences knew her by tells only the opening chapter of a story that deserved far more attention than it ever received.

Born in Peoria, Illinois in 1936, Costello built a career that reflected her strong theater training and ties to The Actors Studio  — a foundation so serious and so deeply rooted in the craft that every performance she gave, whether on a Broadway stage or in a television living room or in the haunting, unforgettable image of a hippie vampire rising from a lake in a wedding dress in the 1971 cult horror film Let’s Scare Jessica to Death , carried the unmistakable weight of someone who had given her entire life to understanding what it meant to fully inhabit another human being. She is survived by her daughter Arin, granddaughter Bird, stepdaughters Amy and Doon, and several nieces and a nephew  — a family that has spoken about her final days with the same quiet grace that defined everything Mariclare Costello ever did, describing a woman who faced the end of a long and extraordinarily full life with the peace of someone who had given everything she had to the work, the people she loved, and the world that was lucky enough to have her in it for ninety years.