Tol Fuin was the largest; Tol Morwen and Tol Himling were much smaller. Tol Himling and Tol Fuin were close to one another, while Tol Morwen was about one-hundred and fifty miles southwest of them.
History
The Western Isles had not always been islands, but places of significance and high elevation in Beleriand before Beleriand sank beneath the Sea at the end of the First Age. Tol Morwen had been, and remained, the location of the Stone of the Hapless marking the graves of Morwen Eledhwen and her son Túrin Turambar. Tol Himling had been Himring, the realm of the eldest of the Sons of Fëanor, Maedhros. Tol Fuin had been a part of the highlands of Dorthonion that were later renamed Taur-nu-Fuin.
After the War of Wrath and the loss of Beleriand, the Western Isles were not known to have ever been inhabited for the rest of the Second Age, Third Age, and beyond.