Dor-lómin was a region in the southwestern part of Hithlum, bordered in the east by the Mountains of Mithrim, and in the north by the river which formed the Rainbow Cleft, also known as Annon-in-Gelydh ("Gate of the Noldor").
Maps
It was first colonized by the Noldor shortly after they arrived in Middle-earth, and for a long time was ruled by Fingon son of Fingolfin, before he took over as High King of the Noldor after his father was killed.
By this time the Edain known as the House of Marach had entered Beleriand, and Hador Lórindol had "entered the household of Fingolfin in his youth and was loved by the King." Fingolfin granted him the land of Dor-lómin as a fief, and he gathered most of his kin into that land.
Húrin's house was built in its southeastern corner near the mountain known as Amon Darthir, where the river Nen Lalaith began.
Tuor son of Huor was fostered by the Elves of Androth in the Mountains of Mithrim, east of Dor-lómin.
After the Nirnaeth Arnoediad ("Battle of Unnumbered Tears"), the House of Hador was destroyed or scattered, and Easterlings dwelt in Dor-lómin.
Like the rest of Hithlum, it was destroyed during the War of Wrath.