After the founding of the Kingdom of Bavaria the state was totally reorganised and, in 1808, divided into 15 administrative districts (Regierungsbezirke (singular Regierungsbezirk)), in Bavaria called (Kreise (singular Kreis)). They were created in the fashion of the French departements, quite even in size and population, and named after their main rivers. In the following years, due to territorial changes (e. g. loss of Tyrol, addition of the Palatinate), the number of districts was reduced to 8. One of these was the Isarkreis (Isar District). In 1837 king Ludwig I of Bavaria renamed the Kreise after historical names, and tribes. This also involved border changes or territorial swaps. Thus, the Isarkreis changed to Upper Bavaria.