Also referred to as the Wilderland, Rhovanion encompassed all of the area bounded by the Misty Mountains to the west, the Grey Mountains to the north, the Sea of Rhun to the east, and the boundaries of Mordor and Gondor at the Ash and White Mountains to the south.

Over its history Rhovanion was populated at one time or another by branches of most of the free peoples of Middle-earth.

In TA 1856 an army of Wainriders from east of the Sea of Rhun took over Rhovanion and enslaved most of its people. They were finally driven away after the Battle of Camp in TA 1944 and never returned.

At the time of the War of the Ring most of Rhovanion was an empty wilderness but it was still populated by the Dwarves of the Lonely Mountain, the elves of Mirkwood and Lothlorien, the Ents of Fangorn, and the Riders of Rohan in the former Gondorian province of Calenardhon.
Encyclopedia entry originally written by PotbellyHairyfoot