Helsinki was founded in 1550 by the Swedish king, King Gustav I.  At that time, Finland was one province in the Kingdom of Sweden. The early years were marred by a series of problems, including disease, poverty and a series of regional wars.  As a result of these problems, Helsinki remained a small backwater for a number of years. It was not until the Suomenlinna Fortress was built on an island off Helsinki, during the mid-1700s, that Helsinki could properly begin to be called a town.

At the beginning of the nineteenth century, Russia defeated Sweden in a war known as the Finnish War, and Finland became a Grand Duchy in the Russian Empire. Almost immediately, in 1812, Tsar Alexander I transferred the capital of the province from Turku to Helsinki, closer to St Petersburg and farther from Stockholm. The sleepy town began to grow into a city. When Turku suffered a disastrous fire in 1827, the University and some other institutions were moved to Helsinki. The main building of the new University of Helsinki and many of the other public buildings near the main market square, all designed in the empire architectural style, date from the mid-1800s.

Industrialization and increased trade led to further growth of the city.  Railroads were established throughout the Grand Duchy, and the population of Helsinki grew steadily throughout the nineteenth and twentieth centuries.  When Finland became independent in December 1917, Helsinki was the logical choice as the new capital. The beginning, however, was not auspicious: at the end of January 1918, the so-called Reds (who had the support of the newly installed Bolshevik government in Russia) declared a revolution, and were able to seize Helsinki along with most of southern Finland. A brief but very bloody Civil War erupted, which did not end until the so-called Whites (with direct German military support) were able to out-fight the Reds and march back into Helsinki, in mid-April 1918. (The so-called Long Bridge, one block south of Hakaniemi Square, still bears scars from artillery and rifle fire.)

Helsinki continued to grow, and its international status received recognition when, only a few years after Finland's independence,  the 1940 Olympics were awarded to Helsinki.  The Second World War forced postponement of those Olympics to 1952. During the Second World War, Finland was at war alongside Germany, and Helsinki bore the brunt of many Soviet bombing raids. Fortunately, the losses from these (in terms of lives and buildings destroyed) remained slight. 

In the years following the Second World War, extensive internal migration in Finland led to very rapid urbanization. From about 275,000 in 1944, Helsinki's population passed the 500,000 mark in the early 1970s.  Today, the Helsinki metropolitan area (the municipalities of Helsinki, Vantaa, Espoo and Kauniainen) has a population of over 1,100,000, or roughly a quarter of the total population of Finland.