Beate Sirota Gordon, the daughter of Russian Jewish parents who at 22 almost single-handedly wrote women’s rights into the Constitution of modern Japan, and then kept silent about it for decades, only to become a feminist heroine there in recent years, died on Sunday at her home in Manhattan. She was 89.

The cause was pancreatic cancer, her daughter, Nicole Gordon, said.

A civilian attached to Gen. Douglas MacArthur’s army of occupation after World War II, Ms. Gordon was one of the last living members of the American team that wrote Japan’s postwar Constitution.

Her work — drafting language that gave women a set of legal rights pertaining to marriage, divorce, property and inheritance that they had long been without in Japan’s feudal society — had an effect on their status that endures to this day.

“It set a basis for a better, a more equal society,” Carol Gluck, a professor of Japanese history at Columbia University, said Monday in a telephone interview. “By just writing those things into the Constitution — our Constitution doesn’t have any of those things — Beate Gordon intervened at a critical moment. And what kind of 22-year-old gets to write a constitution?”