In the First Age the Elves passed through it during the Great Journey, and much later the Atanatári (Fathers of Men) followed them. It is not otherwise mentioned until the Second Age, when it played host to two Silvan Elf kingdoms ruled by Sindarin lords: Northern Greenwood and Lórinand (or Lórien). The great battlefield (or Dagorlad) of the Last alliance of Elves and Men against the host of Sauron lay in the south of Rhovanion, and in the Gladden Fields of the Great River the King of Gondor and Arnor, Isildur son of Elendil was killed.
In the early Third Age, it was a quite populated area: in the north lay the Dwarven kingdom of Erebor and the Mannish kingdom of Dale, in the north of the Great River Anduin lay the Mannish realm of Éothéod, and in and around the south and east of Greenwood the Great lived the Men of Rhovanion. In the north of Greenwood lived the Silvan elves ruled by Thranduil, and in the south of Greenwood and across the river in Lórinand ruled Amdír and later Amroth. In the far south, near the great falls of Sarn Gebir, watched the northern guard of Gondor, and in the valleys of the Anduin lived Stoors (Hobbits).
In the later Third Age, Rhovanion was the site of many wars, when the Wainriders came from the east and assailed the people of Rhovanion until all their kingdoms were destroyed, and later when Sauron returned as the Necromancer he took residence at Dol Guldur in the south of Greenwood. Greenwood became evil, and was renamed Mirkwood. The Dwarves of Eregion and the Men of Dale were destroyed and scattered when the Dragon Smaug took Erebor, and Gondor retreated from the Falls. Some Men still lived along the forest, notably the Bëornings and the Men of Esgaroth upon the Long Lake. The Men of Éothéod removed south at the invite of Gondor, and settled the plains of Calenardhon, later Rohan.
At the end of the Third Age, the Kingdoms of Erebor and Dale were restored as a result of the death of Smaug and the Battle of Five Armies, and Sauron was removed from Mirkwood by the wizard Gandalf. During the War of the Ring it held off an invasion by Sauron's forces, and after Sauron was defeated Mirkwood was clean again, and renamed Eryn Lasgalen, or "Wood of Greenleaves". Some time during the Fourth Age Gondor claimed large parts of it.
Its boundaries were: To the east, the inland Sea of Rhûn. To the north, the Grey Mountains and Iron Hills, home of the Dwarves. To the west, the range of the Hithaeglir, or Misty Mountains. To the south, the line marked by the Limlight river, Anduin, Emyn Muil, Dagorlad, and the Ered Lithui.