Their rule in the Smithlands ended after the events of the Massacre at Hornworth when House Harrigon betrayed them, with Lord Orromus killing King Marthew Smithe. Both the Smithlands and Hornworth have been taken over by the Harrigons.
House Smithe's sigil is a black hammer struck by blue lighting on a red field, a feature later taken by House Harrigon in their sigil. The house's official words are: "Here We Toil".
Before the Targaryen conquest, the leaders of House Smithe ruled over the region as the Kings of Steel and Silver. King Marthew VII Smithe was on the throne during the last years of House Smithe's dominion. After causing the death of Lord Orromus' brother and two of his sons, House Harrigon, with the aid of other houses in the Smithlands, stormed Hornworth and murdered King Marthew. King Marthew's two daughters, Aryana and Allsa, were forcibly married to Orromus, who also took over Hornworth and the title of King. All other living Smithes were either exiled or killed, leaving the Harrigons with full dominion over the Smithlands, ruling as Kings of the Forges until Aegon's Conquest.
King Orromus, instead of wiping out House Smithe's bloodline, instead chose to take parts of their sigil, and took both of King Marthew's daughters to wife, in order to father more heirs as his last revenge on the Smithes. He also took their ancestral sword Greathammer, and melted it down. It is believed that House Harrigon's ancestral weapon Honor's Call, is made from what remains of Greathammer, however the Harrigons still maintain that Honor's Call was created after Aegon's Conquest from the Valyrian Steel Aegon presented to them.
The last living member of House Smithe is Harrin Smithe, an outlaw known as the Orphan King.