Amos Anderson purchased Söderlångvik Manor on Kimito Island in 1927. Additionally, he acquired other large land areas on Kimito Island and its vicinity. In the 1930s, he expanded the single-story log house at Söderlångvik into a mansion-like building. The estate became a beloved place where he spent his summers and where he also passed away, at the age of 82, on April 2, 1961.

Söderlångvik Manor is located in Dragsfjärd at the southern tip of Kimito Island, in a beautiful seaside location. The main building of the estate has been a museum of art and personal history since 1965. Since the late 1970s, art exhibitions have also been held in the old barn, where the cozy Café Söderlångvik offers visitors good food and drinks. Here, you can also purchase farm products and local crafts. In June 2021, the main building reopened its doors after a respectful renovation that lasted two years. After the renovation, the house has regained its former 1930s splendor. A representative selection of artworks from the Amos Rex collections has been placed in the museum, including works acquired by Amos Anderson himself. Additionally, the museum can display most of Anderson's library. The interior is mostly classical, with both antique furniture and replicas of period furniture. From the building, there is a beautiful view of the garden designed by Paul Olsson in the 1930s, which has also been carefully restored.

Amos Anderson's heir, Konstsamfundet, currently owns approximately 7,000 hectares of land, primarily forests and coastal areas in Dragsfjärd and Västanfjärd on Kimito Island, as well as in Pargas. In addition to forestry, the society operates large-scale apple orchards. The plantations at Söderlångvik and Tolfsnäs comprise around 50,000 apple trees after planting in 2021.