Belva Offenberg was a third-generation Jewish American who was raised in New York City.She graduated from Barnard College in 1939 with a degree in history. Plain lived in the Short Hills section of Millburn, New Jersey.
Before breaking into publishing, Belva Plain wrote short stories for magazines while raising her three children. She sold her first story to Cosmopolitan at age 25 and "contributed several dozen to various women's magazines until she had three children in rapid succession." Her first novel, Evergreen, was published in 1978. It topped the New York Times bestseller list for 41 weeks and was made into a TV miniseries. Evergreen followed the character Anna, "a feisty, redheaded Jewish immigrant girl from Poland in turn-of-the-century New York, whose family story continues through several decades and three more books."
At her death, there were over 30 million copies of her twenty-plus novels in print in 22 languages. Twenty-one of her novels appeared on the New York Times bestseller list. Plain did not own a computer, and wrote all of her novels long-hand on a yellow pad. A disciplined worker, she wrote for several hours in the morning five days a week. She produced a 500- or 600-page novel every year or so.