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A Swedish Fortress in 1721–1741

The town of Lappeenranta was founded at the site of the present Fortress in 1649.
The elevated shape of the headland, whose slopes originally descended towards the lake, functioned as a natural fortress even before the construction of the actual fortification structures began.

At the Nystad Treaty of 30 August 1721 following the Great Northern War, the region of South Carelia, including Lappeenranta, remained with Sweden. The Swedes built the first fortification structures on the fortification hill of Lappeenranta in the 1720s. During the years 1738–39, the structures were repaired and replaced. With the imminent threat of a new war, in the summer of 1740 the more extensive armament of the Fortress was initiated.

A Russian Fortress in 1741–1809

During the War of the Hats (1741–1743), in the bloody battle of Lappeenranta of 1741, the Russians conquered the Fortress of Lappeenranta and destroyed parts of the town, but eventually withdrew to their side of the border.

The War of the Hats ended at the Treaty of Åbo of 7 August 1743. A new border was drawn at the River Kymijoki in the south. The region of South Carelia as well as the area around Savonlinna were annexed to Russia. Russia retained the border fortresses of Hamina and Lappeenranta and the old Olavinlinna castle in Savonlinna.

The Russians continued fortification work on the fortress hill of Lappeenranta. In the 1790s, the Fortress of Lappeenranta was made part of the St. Petersburg defence system, under the direction of General Alexander Suvorov. At that time, the so-called Nikolay ramparts were built on the south-western side of the Fortress and the fortifications of Pallo and Kimpinen on the sides of the Fortress.

A Garrison and Prison Area as of 1809

After the Finnish War between Sweden and Russia in 1808–1809, alongside the rest of the so-called Old Finland, the area of South Carelia was annexed to Finland. From 1809 until it gained its independence in 1917, Finland was an autonomous part of the Russian empire, or the Grand Duchy of Finland. At the time, the Fortress of Lappeenranta lost its significance as a border fortress, instead becoming a garrison and prison area.

The construction of a male prison changed the Fortress milieu from 1881 onwards, as did the construction of the Satamatie street and a railway. The last major construction phase occurred before World War I, when several brick buildings were built for Russian troops.

- Pekka Toivanen, The history of the town of Lappeenranta 1649–1743 (in Finnish)
- Raimo Ranta, The history of the town of Lappeenranta 1743–1811 (in Finnish)
- Anu Talka, Pia Puntanen, The history of Lappeenranta 1812–1917 (in Finnish)
- Material of the National Board of Antiquities of Finland
- The Castles and Fortifications project