In 1842, the capital city of Christiania, which at the time consisted of a tiny part of modern Oslo, became a separate subcounty within Akershus main county.

In 1842 the capital city of Christiania, which at the time consisted of a tiny part of modern Oslo, became a separate subcounty within Akershus main county.

After 1948, the remaining Akershus county is conventionally divided into Asker and Bærum to the west of Oslo, Follo and Romerike.

The main national railway lines into Oslo run through Akershus with many junctions and stations such as Asker, Sandvika, Ski, and Lillestrøm.

The county also includes the historical place Eidsvoll, 48 km north of Oslo, in which the national assembly ratified the Norwegian constitution in 1814.

E18 enters Akershus in the south-east, merges for a short stretch with E6 at Vinterbro in Ås, before running under central Oslo.

E18 then turns south-west through Bærum and Asker before entering Buskerud County north of Drammen.

All main railways out of Oslo run through Akershus: Akershus became a fief in the 16th century, and then also included the current counties of Hedmark, Oppland, Buskerud, and Oslo, as well as the municipalities of Askim, Eidsberg, and Trøgstad in the county of Østfold.

In 1768, Hedmark and Oppland were also separated from Akershus to become Oplandenes Amt (and Askim, Eidsberg, and Trøgstad were transferred to Østfold).