From Collins Pocket Reference : Whisky
John Dewar and Sons was one of the blending companies instrumental in the development of new whisky markets outside Scotland. Begun in Perth in 1846, it was the first company to sell its whisky in bottles as well as casks, thus opening up a new market in the home rather than just the licensed shop, pub or hotel. Dewar was also a pioneer of whisky advertising and was one of the first companies whose bottles carried its company name. By the time it became part of the Distillers Company Limited in 1925, it owned seven distilleries, who of which (Aberfeldy and Glen Ord) are still licensed to Dewar. More than 90% of production is exported.
Tasting comment : Dewar's White Label, the bestselling Scotch whisky in the USA, has a slightly smoky aroma and a complex, delicate malty flavour with a clean, dry finish.

-
Source www.bbr.com :

Dewars Distillers

Dewar’s is a famous and widespread brand of blended whisky drawn from distilleries such as Royal Brackla and Craigellachie. However, it is Aberfeldy that allegedly makes up the greater part of the Dewar’s whisky blend.

The company was founded in 1846 by John Dewar, Sr. before passing into the control of his two sons. Ownership currently belongs to Bacardi.

Dewar’s markets the Aberfeldy single malt, along with its blends, the most famous of which is the Dewar’s White Label, which is unusually drunk most commonly in a pint glass, mixed with tap water.

Dewar’s claims to utilise a unique method in its whisky production: double aging, which involves taking the matured spirit at the point where it would normally be bottled and instead placing it in a specifically designated vintage cask for further maturation.