Limited archaeological studies and discoveries indicate that the Gooti tribe has lived there about 4,000 BC. the Kassi or Kassit tribe has immigrated to this region from Caucasia after the Gootis. the Kassis worshipped Souriash or the Goddess of Sun who had Aryan origin. According to valid historical evidences, present Ilam province has been a part of the ancient Elam land.
In Elamite and Babylonian inscriptions, Ilam is called Alamto or Alam which means "mountains" or "the country of sunrise". It has been part of the Achaemenian Empire. Existence of numerous historical vestiges in Lurestan and Ilam provinces belonging to the Sassanide period indicates the specific importance of the region in that time. In the late 4th century AH., Kurdish tribes governed over the region till the early 6th century AH. Between 570-1,006 AH., Atabakan-e-Lor ruled Poshtkooh and Lurestan. Later on, this dynasty transferred their capital to Poshtkooh (present Ilam).
In 1930 AD., in the division of the country, Ilam became a part of Kermanshah province. Then, being a border region and due to important political situation, it was changed into a province and now it is one of the important provinces of the country. Totally, Ilam is a tribal province but in recent years the tribal relations specially the decampment of tribes have changed it drastically.