Following many years of preparation, Ibsenhuset og Grimstad bymuseum (the Ibsen Museum and Grimstad Town Museum) officially opened in 1916. It was the culmination of a local, volunteer-based initiative. The pharmacy in which Henrik Ibsen had worked during the period 1847-50 had been converted to an Ibsen museum. Grimstad's town museum was on the first floor. Numerous enthusiasts were involved in the project. Chief municipal treasurer Karl O. Knudson deserves a special mention. He was also the one steering the museum through the interwar period.
From the 1950s onwards, the museum continued without any permanent employees. There was some activity, but this was dictated by money and time available. The driving force behind the operation during this period was Lisen Ugland Bergshaven. Among the museum's projects was the restoration of Reimanngården, the pharmacy in which Ibsen worked as an apprentice his first three years in Grimstad.
In the 1980s, a decision was made to find a full-time director. The choice fell on local Grimstad man and maritime historian Jarle G. Bjørklund, who led the museum through the 1990s. In collaboration with Bergshav AS in Hasseldalen, a small maritime museum was established, featuring numerous artefacts from the sailing ship era. Temporary positions were also created, primarily to ensure professional handling and recording of items.
At the turn of the millennium, Rolf Erik Nilsen took over as director. The Norwegian museum reform was introduced, and Grimstad's museums came under one administration. This consolidated structure included the Norwegian Museum of Horticulture, established in 1992. With more events taking place, activity increased at the horticultural as well as the town centre museums. The museum foundation was also handed responsibility for the project Grimstad – the Town of Poets. This is an initiative to promote literature, with particular emphasis on Grimstad's two writers of international acclaim; Ibsen and Knut Hamsun.
In 2007, the foundation changed its name: Grimstad bys museer - with Anita Estensen as new General Manager and a team of three permanent employees. The museum foundation holds several collections relating to the town and Ibsen, the maritime museum and the horticultural museum. A collection of old agricultural equipment and carriages (the Birger Beisland's collections) is in storage.
On 01/01/2015, the museum joined forces with AAKS and Setesdalsmuseet to form the new inter-municipal company (IKS) Aust-Agder museum og arkiv.