A descendant of Richard Francis who settled in Cambridge, Massachusetts in 1636, Lydia was a humanitarian.

She was known as one of America's first women of letters, a reformer and novelist who wrote and edited forty books. Her brother Convers was a Unitarian minister who taught at Harvard Divinity School.

Her novel, Hobomok (1824), is the first historical novel published in the United States. Her Appeal in Favor of That Class of Americans Called Africans (1833), persuaded William Ellery Channing and Charles Sumner to oppose slavery. In 1835 her two-volume History of the Condition of Women in Various Ages and Nations voiced her early struggle in this field. She was a founder of the Massachusetts Woman Suffrage Association. Theodore Parker is evident in her three-volume Progress of Religious Ideas, Through Successive Ages (1855), which celebrates world religions.

A biography of Mrs. Child by John Greenleaf Whittier is included in The Letters of Lydia Maria Child (1882). The poet recited a memorial poem at her funeral. Wendell Phillips delivered the oration.