Eorl the Young - "Eorl the Young was lord of the Men of Éothéod.  That land lay near the sources of the Anduin, between the furthest ranges of the Misty Mountains and the northernmost parts of Mirkwood...The people of that region had become few since the Plague, and most of those who remained had been slaughtered by the savage Easterlings.  Cirion, therefore, in reward for his aid, gave Calenardhon between Anduin and Isen to Eorl and his people; and they sent north for their wives and children and their goods and settled in that land.  They named it anew the Riders of the Mark, and they called themselves the Eorlingas; but in Gondor their land was called Rohan, and its people the Rohirrim (that is, the Horse-lords).  Thus Eorl became the first King of the Mark, and he chose for his dwelling a green hill before the feet of the White Mountains that were the south-wall of his land.  There the Rohirrim lived afterwards as free men under their own kings and laws, but in perpetual alliance with Gondor." ~The Return of the King (Appendix A)