Akranes was settled in the 9th century by the brothers Þormóður and Ketill, sons of Bresi, who came from Ireland. The town started to form in the mid-17th century as a fishing village. In 1942, it was formally chartered, and in the following years it had the biggest surge in population in its history.

Industry has been a big and growing employer: a cement plant has been operated in the town since the 1950s, and an aluminum smelting plant has been in operation near the town since 1998.

The fishing industry remains the town's most important source of employment; commerce is also a significant employer, as Akranes acts as a service center for the large rural region surrounding it.

The town is expected to grow further in the coming years because of growing industry and improvements of transportation to the Reykjavík area, following the construction of the 5.57 km-long (3.46 mi) Hvalfjörður Tunnel, which was opened in 1998 and is one of the world's longest underwater road tunnels.