Dragonstone was once the westernmost outpost of the ancient Freehold of Valyria. A century before the Doom, the Targaryen family moved to Dragonstone. When the Doom came upon Valyria, House Targaryen survived along with the last of the Valyrian dragons. Another century later, Aegon Targaryen and his sisters Rhaenys and Visenya launched a massive campaign of conquest from the island and eventually conquered all of Westeros except for Dorne, and North of the Wall. Aegon's progeny reigned as kings of the Seven Kingdoms for centuries.