The town of Helsinki was founded by King Gustav Vasa of Sweden. The date 12.6.1550 is regarded as the date on which the city was founded. Growth was slow, for the medieval trading traditions were slow to change. Due to the wars in Russia, the Baltic countries and Germany, Helsinki was nevertheless a strategic military centre, a point of embarkation for troops and a winter haven for the navy.
In time, the site of the town on the mouth of the River Vantaa proved unfavourable, and in 1640 a decision was made to move it further south to the Vironniemi headland, nowadays known as Kruununhaka near the city centre. Russia's growing power in the 18th century and the founding of its new capital, St. Petersburg, not far from the Finnish border in 1703 were to have a decisive influence on the growth and future of the Finnish capital. The century was, however, one of great hardships for Finland and Helsinki, which suffered gravely from war, plague and hunger. The Russians occupied Helsinki in 1713-21 and again in 1742. Sweden lost its status as a superpower.
The war having been lost, it became vital for Sweden to fortify Helsinki. In 1748, construction of the magnificent sea fortress of Suomenlinna, built on an outlying island, was begun, creating what was described by a historian of the time as the «Gibraltar of the North.» The building of Suomenlinna marked a turning point in the history of Helsinki, bringing prosperity to the town.
Finland was annexed to Russia as an Autonomous Grand Duchy in 1809. Helsinki was proclaimed the Finnish capital in 1812 and Finland's only university, which had been founded in Turku in 1640, was transferred to Helsinki in 1812.
Devastated by fire, the town was completely rebuilt in a style worthy of a capital. Helsinki soon became an administrative, university and garrison town, and the biggest industrial city in the land. By the beginning of the 20th century it had a population of over 100,000.