The manor of Ekolsund was established in the 1300s. The first known owner was the council Magnus Knutsson, mentioned in 1351. In the 1500s the castle came into royal hands when King Gustav Vasa took over the ownership. It was in 1578-1611 the residence of Princess Sophia of Sweden.
The crown anyway donated Ekolsund to Åke Tott in 1618. Ekolsund was moved again to the Crown during Karl XI’s reduction, and in 1716 it was appointed to Landgraf Fredrik of Hessen-Kassel (later Fredik I). In 1747 it was sold to Prince Adolf Fredrik on the account of the new heir Gustav (later Gustav III). In 1785, Ekolsund was sold from the hands of the Crown to George Seton, a man of Scotish heritage. In 1917 it was bought by Carl Kempe. In 2002, Ekolsund was bought by a private firm.
Both southern and northern castle was built in the middle of the 1600s, excedran came centuries later. Architects were Simon de la Vallée, Nicodemus Tessin the Elder, Carl Harleman, Carl Fredrik Adelcrantz and Jean Eric Rehn.
References:Towering 52 meters above the sea, Bengtskär lighthouse is the tallest one in Scandinavia. The building started in in 1905 after the shipwreck of S/S Helsingfors and was completed in 1906. The lighthouse was designed by architect Florentin Granholm. On December a special petrol lantern, designed and built in Paris, was brought to Bengtskär and installed atop the tower.
German fleet bombarded Bengstkär in the First World War in 1914. Since the Gulf of Finland was heavily mined, it was not until 1919 that the surrounding seas were declared safe for shipping, that the light was lit again.
After the war the military value of Bengtskär increased as part of the defence system of independent Finland. In Second World War (1941) Soviet Union made a suprise attack to island. After a bloody battle, the small Finnish garrison emerged victorious. Intermittent repairs to the facility continued during the post-war period.