During the Middle Ages, 90 per cent of Sweden ´s population were peasants. Most of them lived on isolated farms in the forests. On the plains, though, there were villages. About the half of the peasants were freeholders and paid tax to the King. The other peasants leased their farm-land from the aristocracy or the Church.
The provinces of Skåne, Blekinge and Halland belonged to Denmark, except for the years 1332-1360 when Skåne and Blekinge were Swedish. Bohuslän, Jämtland and Härjedalen belonged to Norway. Gotland was Danish from the year 1361.
The aristocracy and the King competed for power during the greater part of the Middle Ages. In the 13th century, the Crown established castles in order to rule the country more efficiently. Towns were founded to make trade easier and to make profits from it.
Stockholm was the largest town during the Middle Ages. Other important towns were Kalmar, which was a southern frontier stronghold, Viborg, which protected the eastern border and Lödöse (preceding Göteborg) giving the country access to the North Sea. In the larger towns, there were a lot of German merchants.
The effects of the Black Death caused a severe crisis in farming during the second half of the 14th century. A third of the population may have died and many farms were left abandoned.
The strong German influence in the Baltic region was the main reason for establishing a union between Sweden, Denmark and Norway. The Kalmar Union was founded in Kalmar in the summer of 1397. At the same time, Erik of Pommern was crowned King of these three countries. Sweden left the Union in the middle of the 15th century, but it was re-established during short periods at the end of the 15th and beginning of the 16th centuries.
St. Bridget founded a convent in Vadstena, which became a centre for culture and education during the 15th century. The patron saint of Sweden is St. Eric, a 12th-century king not to be confused with Eric of Pomerania.