From the book 'Collins Pocket Reference' Whisky :
Tullamore Distillery, Tullamore, Co. Offaly
Tullamore Distillery was founded in 1829, well placed in the Midlands for distributing its produce via the Grand Canal. Throughout its history the distillery has been renowned for producing the lightest and most accessible of Irish whiskies, a tradition carried on today. But with the rest of the industry in Ireland, Tullamore died a slow death into the mid twentieth century. Its decline was offset by the success of its Irish Mist liqueur, but the distillery, still with plenty of stocks, closed in 1954. Since then it has been gradually demolished. Its products were bought by Power & Son in 1965, passing with it the following year into the Irish Distillers Group. In 1994 the business was sold on again to C&C International, part of Allied Domecq.

Tullamore Dew Co. Ltd, Tullamore, Co. Offaly
Tullamore Distillery no longer exsist as a whiskey-producing centre, but the name of its moust famous whiskey lives on in a new incarnation which is one of the most Irish whiskies in Europe. The distillery was originally founded in 1829 by Michael Molloy, but by the late 1880s was under the co-owner-ship and control of Daniel E. Williams, who had worked at the distillery from his boyhood. His initials were the insparation for the name of the company's most famous product and, in turn, for the deathless advertising slogan still featured on every bottle, 'Give Every Man His Dew'. The distillery fell victim to the recession in the Irish whiskey industry in the mid twentieth century, and today Tullamore Dew is produced in Co. Cork at Midleton Distillery.

-
Source www.bbr.com :

Tullamore Dew Distillery

Tullamore Dew is one of Ireland's whiskey distilleries, first produced in 1829 in the small town of Tullamore in County Offaly in the heart of Ireland. The name derives from the initials of an early owner, Daniel E Williams - DEW. Connoisseurs describe Tullamore Dew as... "Subtle, smooth and with a pleasant maltiness combined with charred wood undertones and the natural flavour of golden barley."

The Tullamore Dew range comprises of Tullamore Dew Original, Tullamore Dew 10-Year-Old Reserve, Tullamore Dew 12-Year-Old Special Reserve and the Heritage Blend.