Odal (Odalen) is a valley in the county of Hedmark in eastern Norway, encompassing the communities around lake Storsjø in the north, with the river Glåma in the south. It is part of the traditional region of Odalen. The district is currently divided between the two municipalities of Sør-Odal and Nord-Odal which were split into separate municipalities in 1819. A person from Odalen is commonly called a odøling.
Glommadal (Glåmdalen) is a designation for the valley formed by the river Glåma (also called the Glomma), which is the longest and largest river in Norway. From Lake Aursund in the north on south to Elverum, the valley is called the Østerdalen. From that point south until Kongsvinger, it is referred to as Solør. As it turns westerly from Kongsvinger until Nes, it is called the Odalen. These designations are traditional districts, reflecting the designations locals used for their valleys.
Odalen is a landscape name derived from the old Norwegian name Ódalr. Ó or À, which means "river", here the Glåma river. The last element is dalr which means "valley" or "dale". The name can be documented to have been in use since 1386. Traces of human habitation dating back to the Nordic Bronze Age, between 1500 and 500 BCE. The first farms were probably cleared close to the lake about 500 BCE, in the early Iron Age. Settlement spread slowly around the lake and inland, and by the year 800, there may have been as many as 50 farms in the area. Settlement accelerated in the Viking Era, increasing the number of farms by as much as an order of magnitude. Increased mobility in the Norwegian population likely changed the character of the society in Odalen, and there is evidence the area was under the administration of the Thing in Eidsvoll.
When the region was Christianized around 1030, several churches were built, including locations at Oppstad, Strøm, Ulleren, Mo and Trøftskogen. The area became politically more autonomous. The valley may have become overpopulated until the Black Plague and following plagues, when a huge proportion of the population died. Farms were abandoned and consolidated during this time, and it took at least 200 years for the population to reach its previous levels. In the 17th century, Odalen suffered economic setbacks as a result of taxation and general economic downturns. Forestry rose as a complementary source of income to agriculture. By all accounts, the agricultural sector has not grown appreciably in the area since the 18th century. Trautgruva iron ore mine was operated until 1830.