<P> On his death, he left approximately half of his huge estate to The Duke Endowment, which gave another $67 million (equivalent to $934,948,767 in 2017) to the trust fund . In the indenture of trust, Duke specified that he wanted the endowment to support Duke University, Davidson College, Furman University, Johnson C. Smith University; not - for - profit hospitals and children's homes in the two Carolinas; and rural United Methodist churches in North Carolina, retired pastors, and their surviving families . </P> <P> The remainder of Duke's estate, estimated at approximately $100 million (equivalent to $1,395,445,920 in 2017), went to his twelve - year - old daughter, Doris, making her "the richest girl in the world". Doris sued her mother for control of the Duke Farms estate and won . Associating Duke Farms with fond memories of her father, Doris Duke made few major changes to the property other than the adaptation of her father's Conservatory to create Display Gardens in his honor . These gardens showcased her father's extensive sculpture collection and were open to the public from 1964 until closed by her foundation trustees in May 2008 . </P>

How did the duke family make their money