The Seven Kingdoms are frequently mentioned on HBO's medieval-fantasy drama, Game of Thrones, and its prequel, House of the Dragon. The Warden of the North and Lord of Winterfell, Eddard Stark was the first to drop the name in Game of Thrones season 1, episode 1 "Winter Is Coming," while executing a deserter of the Night's Watch in the name of Lord of the Seven Kingdoms, King Robert I Baratheon. His sentence conveyed that he took care of North for a man who not only was the King of the Seven Kingdoms but also the protector of the realm. While North was one of the Seven Kingdoms, six more were gradually introduced on the screen.
Shortly afterward, Game of Thrones mentioned King's Landing as the capital of the Seven Kingdoms headed by a figure on the Iron Throne, located in the Great Hall of the Red Keep. This throne was allegedly forged with a thousand swords and knives of Aegon the Conqueror's enemies during his conquest of the continent of Westeros. Aegon I, in fact, was the founder of the erstwhile ruling Targaryen Dynasty of Westeros, the first Lord of the Seven Kingdoms, and the king on the Iron Throne. He was born in 27 BC on Dragonstone, and he and his sister-wives (Visenya and Rhaenys) landed with a small army on the eastern coast of Westeros in the Crownlands, north of where the Blackwater Rush flows into Blackwater Bay. Before his landing, the Lord of Dragonstone, Aegon I sent forth ravens to every lord in the Seven Kingdoms, demanding their fealty, and declaring his paramountcy.
The Kingdoms At The Time Of Aegon's Conquest
Aegon who initiated the War of Conquest 300 years prior to the events of Game of Thrones, was able to seek the subjugation of six independent Kingdoms except for the Principality of Dorne ruled by House Martell of Sunspear. The subjugated were the North ruled by House Stark of Winterfell, the Westerlands ruled by House Lannister of Casterly Rock, the neighboring Reach ruled by House Gardener of Highgarden, the Iron Islands and the Riverlands ruled by House Hoare of Harrenhal, the Stormlands ruled by House Durrandon of Storm's End, the Mountain and the Vale ruled by House Arryn of the Eyrie.
The Lannisters (led by Lord Tywin on Game of Thrones) in the Kingdom of the Rock and the Gardeners in the neighboring Kingdom of the Reach formed an alliance and provided stiff resistance against Aegon Targaryen. Nicknamed the Two Kings, Loren I Lannister and Mern IX Gardener commanded a combined host of fifty-five thousand men to fight Aegon the Conqueror in a battle known as Field of Fire. While Aegon's side didn't have the numbers, he had three fire-breathing dragons that torched enemy formations and mortally wounded King Mern IX Gardener and his kin. In the aftermath, the Reach was given to the Gardener stewards, the Tyrells, as their High Steward, Harlen Tyrell surrendered Highgarden to Aegon.
Aegon's Conquest (a potential Game of Thrones prequel) had far-reaching repercussions on the Kingdom of the Isles and the Rivers and the Stormlands. Aegon's fiercest commander and rumored bastard half-brother, Orys Baratheon slayed the last Storm King Argilac Durrandon in the Last Storm, married his only living heir, Argella, and established House Baratheon. House Hoare was destroyed in the Burning of Harrenhal, and the Iron Islands and the Riverlands were bifurcated into two separately administered regions. House Tully was granted the Lord Paramouncy of the Riverlands for supporting Aegon, and House Greyjoy assumed control of the Iron Islands, bringing the total to eight. Furthermore, the Crownlands is the ninth constituent region of the Seven Kingdoms. Aegon took control of the region during the Conquest and made it his primary foothold in Westeros. The Crownlands is ruled directly by the Iron Throne instead of a Lord Paramount.
The Saga Of Dorne And North's Independence
By the end of the Conquest, Houses Lannister, Stark (led by Eddard Stark on Game of Thrones), and Arryn upheld their legacy as the Great Houses, whereas Orys formed House Baratheon and House Tyrell's status was elevated. Aegon was anointed at the Starry Sept by the High Septon with the seven oils and proclaimed "Aegon of House Targaryen, the First of His Name, King of the Andals, the Rhoynar, and the First Men, Lord of the Seven Kingdoms, and Protector of the Realm." This coronation signified that Aegon I's reign had officially begun. While he was recognized as the ruler of the Seven Kingdoms, the fact is, Princess Meria Martell's Dorne still remained out of the fold. The Dornish guerrilla warriors continued to resist the Targaryen invasion until a marriage alliance was forged in 187 AC. Dorne was formally made part of the realm through the marriage between Princess Daenerys Targaryen and Prince Maron Martell at King's Landing.
Aegon took the existing Kingdoms and forged them into a realm. While the Crownlands and the Riverlands aren't technically their own Kingdom, the monarch on the Iron Throne was the paramount ruler of all nine constituent regions. Despite using the nomenclature of Seven Kingdoms, the nine distinct regions of Westeros (as depicted on Game of Thrones) are the North, the Vale, the Riverlands, the Iron Islands, the Westerlands, the Crownlands, the Reach, the Stormlands, and Dorne. Game of Thrones season 8, episode 6 "The Iron Throne," saw Sansa demand independence North at the Great Council of 305 AC. Her brother, Bran gave his assent and North became an independent Kingdom as it was for thousands of years before the Targaryen invasion. At the end of Game of Thrones, Sansa was crowned as Queen in the North, and Bran the Broken was hailed as Lord of the Six Kingdoms.