Rowntree’s was founded in York in 1862 by Henry Isaac Rowntree, who bought a chocolate company from the Tuke family.  In 1869, he was joined by his brother, the philanthropist Joseph Rowntree.  The original factory was in the centre of the City of York, by the River Ouse at Tanners Moat, but was relocated in 1906 to Haxby Road in the north of the City.

The Company merged with Mackintosh’s in 1969, to become Rowntree Mackintosh.  Rowntree was responsible for such chocolate favourites as Kit Kat,Smarties, Aero, Fruit Pastilles and Black Magic,  while John Mackintosh and Co. produced Rolo, Munchies, Caramac and Quality Street.  The same year, Hershey entered a licensing agreement with Rowntree Mackintosh to introduce Kit Kat and Rolo in the United States.

Info gleaned from Wikipedia