The old municipality of Rana was divided into Mo (until 1844 named Nord-Rana) and Hemnes (until 1844 named Sør-Rana) in 1839. The village of Mo (see Mo i Rana) was separated from the rural district as a town and municipality of its own January 1, 1923 - and the rural district then changed the name back to Nord-Rana. The town of Mo was again merged with Nord-Rana January 1, 1964 - and the united municipality then changed the name to Rana.
The municipality is the third most populous in the region North Norway. By area, Rana is the largest municipality in Norway south of Finnmark, taking in large areas of mountains and forested valleys. Mo i Rana houses the National Library of Norway.
The municipality is located just south of the Arctic circle, on the southern side of the Saltfjellet mountains with the Svartisen glacier, Norway's second largest glacier. Mo is so close to the Arctic Circle that parts of the sun is continuously over the horizon (Midnight sun) from early June to early July, and there is no darkness from mid-May to the beginning of August (). The Saltfjellet-Svartisen National Park is partly located in Rana. There are many valleys, the longest is Dunderlandsdal. The majority of the population in the municipality lives in Mo i Rana, where the Ranelva (river) meets the Ranfjord. North of the Mo i Rana, European route E6 pass through the urban district of Selfors. Rana and Saltfjellet is famous for its numerous caves due to the limestone rock. There are several nature reserves in the municipality, such as Alterhaug with several warmth loving plants including elm (), Engasjyen, the estuary of the Rana river with its rich bird life in spring (), Blakkådalen with old growth spruce forest () and Fisktjørna, with largely undisturbed mixed old growth forest with unusually rich plant life due to the extremely lime rich soil (). There are many lakes in the municipality, both in the lowlands and in the mountains.