The St. Henry's Chapel is a medieval wooden barn, which was surrounded by the present brick chapel in 1857. According the legend St. Henry, the first bishop of Finland, spent his last night in the barn before local peasant Lalli murdered him in 1156. Although according modern archeological investigations oldest parts of the barn were made in 1472-1473. Oldest records from the 17th century tells that the barn has been a destination for local pilgrimages.
Senate of Finland decided to protect the barn as the national heritage in 1839. Architect Pehr Johan Gylich designed the chapel around barn to shelter it. The chapel was inaugurated in 1857.
The chapel is open to the public in July with no admission fee.
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.