The Slughorns were included in the Pure-Blood Directory (published anonymously in Britain, although widely believed to have been authored by Cantankerus Nott), which listed them as one of the twenty-eight truly pure-blood families (the so-called 'Sacred Twenty-Eight'). While according some value to their blood purity, the Slughorns were not overly prejudiced against Muggle-born or Half-blood. They were also considered very wealthy.
Among the family members was Horace Slughorn, Potions master and Head of Slytherin House in the 1940s and after a period of retirement, again in the late 1990s. His father was a high ranking Ministry official at the Department of International Magical Co-operation. He and his wife had both died by the time Horace retired in late 1981.
Even though Horace had no children of his own, the Slughorn family continued through another related line.