The first evidence of Pyhtää as an independent parish dates back to 1380. At that time already the parish had a church, but it is not known where it was situated or what it looked like. Until 1600 Pyhtää included, besides its present area, also half of the present city of Kotka, Ruotsinpyhtää, Elimäki, the western parts of Anjalankoski, and a part of Lapinjärvi.
Dedicated to St. Henry, the church is situated where one of the westernmost branches of the river Kymi meets the ancient Turku-Viipuri coast road.
The building resembles the majority of the Finnish medieval stone churches. Pyhtää church, built about 1460, has retained its original medieval appearance almost untouched. There have been few alterations: the porch was converted into a memorial choir during the latter half of the 18th century, and in connection with repairs in 1907, buttresses were built to support the north wall and the sacristy was fitted with the outer entrance.
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.