She was a daughter of Charles Calvert, 5th Baron Baltimore, and wife Mary Janssen.
The Barons Baltimore were lords proprietors of the Maryland Colony of British America, granting them semi-feudal control of the province, including the right to collect taxes, establish courts and appoint the governor.
However, Governor Robert Eden disputed Harford's inheritance, and in 1774 tried to claim a part of the estate on behalf of his wife Caroline.
Caroline Eden would however lose her claim - Harford succeeded in winning his father's inheritance; the rents from the Calvert estates in Britain were awarded to Harford by an act of Parliament - Lord Baltimore's Estate Act 1781 (21 Geo.
But in 1781 the new State of Maryland confiscated all of Henry Harford's estates and used their income to help finance the cash-strapped revolutionary government and its militia.