You can find information about the Ramapo Mtn. region at several internet sites.Here is a short description:
According to the first part of the legend, the first settlers in the Ramapo Mountain region were Tuscarora Indians. They fled northward on the Cumberland Trail to join their allies the Iroquois in upper New York after a humiliating defeat at the hands of the British Army in a series of skirmishes, part of the French and Indian Wars, in western North Carolina from 1711 to 1714. They were either joined shortly after their arrival by or came accompanied with runaway slaves, often referred to in those days as "Jacks." The sons of Black freedmen from the plantations of the nearby Hudson River Valley and Catskill Mountains also joined them and brought their former masters' Dutch surnames with them to the Ramapos. They intermarried with the Tuscaroras and possibly local Lenni Lenape Indians, as well. It is at this time that their local neighbors may have begun to refer to these people as the "Jacks and Whites."
According to the second part of the legend, during the War of Independence, the British Army command at New York contracted with a Colonial seacaptain and trader named Jackson to bring 3,500 prostitutes recruited in the cities of England to New York to serve the garrison. On the trans-Atlantic voyage one of the twenty ships in the convoy foundered during a storm and most of the passengers were drowned. The clever and industrious Jackson made for the West Indies and picked up an additional 400 black women to replace those lost at sea.
On his return to New York harbor the black prostitutes, known ironically as "Jackson Whites" and as "Jackson Blacks," were segregated from the rest and billeted for several years in a cow pasture in Greenwich Village called Lispenard's Meadows. When the British were forced, abruptly, to quit New York during the War of Independence, the women fled Manhattan in fear of their lives and wandered northward into the Hudson Valley where they heard, possibly from Hessian deserters, that the Ramapos were a haven for Tory refugees, Dutch adventurers and villians of all kinds, including the infamous Tory guerilla Cladius Smith, Cowboy of the Ramapos. and his followers and admirers.
All these people, according to legend, wound up in the Ramapos and by 1800 were firmly ensconced as a clannish, isolated group bearing the collective name "Jackson Whites," presumably as an ironic variant of "Jacks and Whites." The were despised by their respectable lowland neighbors either for having been Tory sympathizers, for their mixed blood, or for being Black, or Indian, or outlaw, or all of that, and more. From roughly 1800 on, the Jackson Whites had little to do with the world outside their Ramapo Mountains retreat and the few towns and villages they had managed to build.