House Strong of Harrenhal was an ancient line of the riverlands that boasted descent from the First Men. The seat of their early years has been lost to record, but the family was already old when the dragons came west: during Aegon's Conquest they followed House Tully in rebelling against Harren Hoare, and as the ironborn cowered in Harrenhal, Harren is said to have offered the hand of a Strong daughter to any man who could slay Balerion. After the Conquest, Ser Osmund Strong served as Hand of the King to Aegon I and oversaw the raising of the wall that still encloses King's Landing.
Their fortunes turned on Ser Lucamore Strong, called Lucamore the Lusty, who won the grand melee at the tourney for the completion of the Dragonpit in 55 AC and took the white cloak under Jaehaerys I. In 73 AC, after the death of Queen Rhaena Targaryen, the Old King named Lucamore's brother Ser Bywin Strong as Lord of Harrenhal, and so the house came to its great seat. Lord Lyonel Strong served Viserys I as master of laws and later as Hand of the King; his elder son, Ser Harwin "Breakbones," was sworn shield to Princess Rhaenyra Targaryen and the rumored true father of her three Velaryon sons, while his younger, Larys "Clubfoot," sat among the king's confessors. In 120 AC, Lyonel and Harwin perished together in a mysterious fire at Harrenhal, and Larys succeeded as lord, master of whisperers, and Lord Confessor.
The Dance of the Dragons unmade them. Larys sat the green council of Aegon II while his great-uncle Ser Simon Strong held Harrenhal as castellan; when Prince Daemon Targaryen took the castle, Simon and his grandsons were captured, and after Ser Criston Cole recovered it, Prince Aemond Targaryen put Simon, his grandsons, and every other Strong he could find, trueborn and baseborn alike, to the sword. Larys himself was executed by Lord Cregan Stark during the Hour of the Wolf in 131 AC, accused of betraying his king, and so the line was ended. Harrenhal passed to House Lothston in 151 AC, and by the time of A Game of Thrones only a handful of men in the Golden Company still wore the name, claiming descent that no one alive could prove.