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
1979 advert for Aero chocolate bar.
The Aero bar was originally introduced in the North of England in 1935 by the Rowntree Mackintosh chocolate company in York, one of the first products in a new marketing-led sales initiative introduced by the company during the 1930s. Distribution was increased to the rest of the UK during the following months. Rowntree Mackintosh was acquired by Nestlé in 1988, who continued the production of the Aero brand.