National Women’s History Month has origins in New York City, where the Social Democratic Women’s Society first observed National Woman’s Day in 1909. That expanded to “Women’s History Week” due to work by educators in Santa Rosa, California, who initiated the week-long observance in 1978. The date in March was chosen to include International Women’s Day, March 8, which has been observed by the United Nations since 1975.
Through the work of women's organizations and educators, observance spread across the country. By 1986, fourteen states celebrated Women's History Month. In 1987, Congress designated March as National Women's History Month in perpetuity.