 He inherited the Penrhyn Estate near Bangor in north-west Wales through his wife's father, George Hay Dawkins-Pennant, and changed his name to Douglas-Pennant by Royal licence in 1841.Lord Penrhyn was the owner of the Penrhyn Quarry near Bethesda, Wales, which under his ownership developed into one of the two largest slate quarries in the world.He was also involved in politics and sat as Member of Parliament for Caernarvonshire between 1841 and 1866.