Eorl was the first King of the Mark. He ruled for 35 years, from 2510 to 2545. Eorl chose the hill at the entrance to the valley of Harrowdale in the White Mountains as the site for the capital city of Edoras. But the Golden Hall of Meduseld was not built in his lifetime, and he dwelled at Aldburg in the Folde.

The Easterlings launched a series of attacks along the Anduin and in the Emyn Muil on Rohan's eastern border. In 2545, Eorl was killed in battle with the Easterlings in the Wold. He was buried in a mound at the foot of the hill where Edoras stood.

Eorl was succeeded by his son Brego. Brego drove the Easterlings out of the Wold. He also began to push back the Dunlendings - a race of Men from west of the Misty Mountains who had infiltrated Rohan over the River Isen.

Meduseld was built during Brego's reign. The great hall was completed in 2569. At the celebratory feast, Brego's son Baldor announced that he intended to enter the Paths of the Dead. Brego and Baldor had found the Dark Door while exploring Harrowdale, and they had met an old man who told them that the tunnels beyond were haunted by the Dead. Baldor entered the Paths of the Dead in 2570 and never returned. Brego died of grief shortly afterwards.

Brego's second son Aldor became King. He was known as Aldor the Old, and he had the longest reign of any King of Rohan - 75 years from 2570 to 2645. Aldor drove out the last of the Dunlendings, who came to hate the Rohirrim. During Aldor's reign, the population of Rohan increased and the Rohirrim settled in the valleys of the White Mountains including Harrowdale.

Aldor's son Frea was old when he became King and he ruled only 14 years until 2659. Frea was followed by his son Freawine, who in turn was succeeded by his son Goldwine. Rohan was peaceful and prosperous during this time.

Deor, son of Goldwine, became king in 2699. During his reign, the Dunlendings began to raid the Westfold to steal horses. Many came across the River Isen, but it soon became apparent some Dunlendings had made settlements in the northern part of the Westfold near Fangorn and Isengard. In 2710, Deor led a force to the northern Westfold and defeated an army of Dunlendings.

Deor proceeded to Isengard and found that it was occupied by Dunlendings. The stronghold belonged to Gondor, but over time the Gondorian chieftains who guarded it had died out and had been succeeded by chieftains of mixed blood who were friendly to the Dunlendings. The few remaining guards had been killed, and the Dunlendings occupied the Ring of Isengard. Deor sent to Gondor for aid, but no help could be spared. The Rohirrim did not have the resources to retake Isengard, so Deor set up a guard of Riders to keep watch in the northern Westfold. Deor was succeeded by his son Gram in 2718.

Helm, son of Gram, became King of Rohan in 2741. Rohan was invaded by the Dunlendings during his reign. A Man of Rohan named Freca, who had Dunlendish blood, began to expand his own domain on the border between Rohan and Dunland in defiance of the King's rule. At a council meeting in 2754, Freca sought a marriage between his son Wulf and King Helm's daughter. Helm refused, and when Freca became enraged and insulted the King, Helm slew him with one blow from his mighty fist. Thus he became known as Helm Hammerhand.

Freca's son Wulf led the Dunlendings to invade Rohan four years later in 2758. The Dunlendings were aided by the Corsairs, who had launched a massive assault against Gondor at the same time. Rohan was also invaded by enemies from the East.

The Dunlendings overran Rohan and captured Edoras. Helm's son Haleth died defending the doors of Meduseld, and Wulf sat on the throne in the Golden Hall. Helm was driven back from the Crossings of the Isen to the stronghold in the Deeping-coomb that became known as Helm's Deep. Many other Rohirrim took refuge there and in other valleys of the White Mountains, including Harrowdale where Helm's nephew Frealaf defended the stronghold of Dunharrow.