 Finland declared independence from Russia in 1917, at the time of the Russian Revolution.These historical factors have had a significant bearing on the history of architecture in Finland, along with the founding of towns and the building of castles and fortresses (in the numerous wars between Sweden and Russia fought in Finland), as well as the availability of building materials and craftsmanship and, later on, government policy on issues such as housing and public buildings.As an essentially forested region, timber has been the natural building material, while the hardness of the local stone (predominantly granite) initially made it difficult to work, and the manufacture of brick was rare before the mid-19th century.