Anna Hempstead Branch was born in New London in 1875 to the poet Mary Lidia Bolles Branch and her husband John Locke Branch. Though she spent much of her youth in New York City where her father practiced law, Anna maintained a strong attachment to the city of her birth. This was due in no small part to her ancestry, which included many of the most prominent families of Southeast Connecticut, and her family homestead, the Hempstead Houses, among the oldest houses in Connecticut.

Because there was as yet no women's college in New London, Anna left home for Smith College in 1893. Though she made some attempts at writing in publishing prior to college, it was at Smith that she began to devote herself to poetry. In 1898 she won a competition held by Century Magazine for the best poem by a recent college graduate. She followed this success with regular publication in national magazines. Her first of four collections was published by Houghton Mifflin in 1901.

Anna lived much of her life in New York City where she participated in literary life and volunteered at the Lower East Side settlement house, Christodora House. There she formed the Poets' Guild to teach classes, form writing groups, and encourage the residents of the area tenements in their poetic efforts. She brought in other poets to support the Guild, including Pulitzer prize winners E.A. Robinson, Margaret Widdimer, and William Rose Benét.