Minhiriath was located in Eriador, covering the western half of the lands between the Misty Mountains and the Blue Mountains (Ered Luin). Minhiriath had no clear border in the north, but to the south, and east and west it was bounded by river and sea: the Brandywine, the Greyflood and the Belegaer, 'The Great Sea'.
The original inhabitants of Minhiriath (Minhiriathrim) were descended from the same Men as the ancestors of the Númenóreans, but because they spoke mutually unintelligible languages, the Númenóreans did not class the Minhiriathrim as Middle Men.
When the large-scale deforestation of their land began under the Númenórean 'Ship Kings' after the 7th century Second Age, the Minhiriathrim became openly hostile, and were persecuted. Only those who "fled from Minhiriath into the dark woods of the great Cape of Eryn Vorn" survived. Most, if not all of these forest-dwellers subsequently "welcomed Sauron and hoped for his victory over the Men of the Sea", but they were to be disappointed - and permanently trapped - by Sauron's burning of much of the rest of the surviving forest, and final defeat, in SA 1701.
From SA 3320, Minhiriath became nominally part of the newly established Kingdom of Arnor, at which time it formed the upper part of ..a land that was far and wide, on either bank a desert, treeless but untilled.
('The History of Galadriel and Celeborn' from Unfinished Tales)
From TA 861, Minhiriath was inherited by one of Arnor's three successor states, Cardolan, but the "ravaging" of Cardolan by the evil forces of the Witch-king of Angmar in TA 1409 no doubt caused extensive depopulation of the whole country. Even worse was the advent of the Great Plague in TA 1636, after which Minhiriath was "almost entirely deserted". After TA 1975, even though "a few secretive hunter-folk lived in the woods" throughout the Third Age (probably a reference which includes Eryn Vorn), Minhiriath was claimed by no kingdom at all.
Although "still in places well-wooded" by the time of the War of the Ring, the once continuously forested Minhiriath bore the permanent scars of over 5000 years of felling, burning, and war.
The same is not necessarily the case for its human population, however, when talking of Eriador (and particularly the lands south and west of Bree) to an innkeeper at the end of the War of the Ring. For example, Gandalf confidently predicts that ..the waste in time will be waste no longer, and there will be people and fields where once there was wilderness.
("The Journey Home", The Lord of the Rings)
Places of Middle-earth and Arda
Forests & Mountains:
The rest of Arda: