出生于宾夕法尼亚州默瑟斯堡., 1830年,11岁时成为孤儿, 哈里特·莱恩由她的单身汉叔叔詹姆斯·布坎南抚养长大(她称他为“Nunc”). 当布坎南成为国务卿时, she attended Georgetown Visitation Convent; when he served as minister to Great Britain, she traveled abroad with him; and when he became the 15th president of the United States in 1857, 她成了他的第一夫人.