Living in Pennsylvania during the American Revolution, he actively supported U.S. independence by founding the Philadelphia Light Horse, now known as the First City Troop, and presenting them with a regimental flag of thirteen stripes to represent the thirteen rebel colonies.
His grandfather, Pierre Marcou, a French Huguenot, had left France for the Danish West Indies before the revocation of the Edict of Nantes.
[1][3] In St. Croix, Markoe became rich by inheriting his father's sugar plantations and trading with both American colonies and Europe.
He married a widow, Elizabeth (Kenny) Rogers, in 1751, and had two sons, Peter and Abraham Jr.
Abraham Markoe Jr., stayed in St. Croix to manage the family sugar plantations.