The ironworks in Kimo was founded by Petter Heijke in 1703. Petter Heijke chose the place because there was an enough deep harbour in Oravainen, waterpower and wood for making charcoal. The ore was brought from Utö in the southern Baltic sea and from Herräng mines in Roslagen. In Kimo it was forged into iron-pigs. The iron-pigs were then tranported further up the river to the forges in Kimo where it was refined into iron-bars.
Kimo was acquired by captain Lars Magnus Björkman in 1818. He renewed ironworks strongly and built for example a lighthouse to the Stubben island. Iron manufacturing ended in 1890s and the factory site started textile business. The heyday of textile manufacturing in Oravainen was in 1920s-1930s.
The original ironworks site and buildings are well-preserved. Today the Kimo Ironworks includes three hammersmith´s workshops: the Lower Mill, the Middle Mill and the Upper Mill. The Lower Mill is the centre of the museum exhibiting the the iron manufacturing. The museum and art gallery are open on order or when there are events arranged on the site. There are also a café and restaurant. Several events are arranged in the ironworks area during the summer season.
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.