Lahti was first mentioned in documents in 1445. The village belonged to the parish of Hollola and was located at the medieval trade route of Ylinen Viipurintie, which linked the towns of Hämeenlinna and Vyborg.
The completion of the Riihimäki – St. Petersburg railway line in 1870 and the Vesijärvi canal in 1871 turned Lahti into a lively station, and industrial installations began to spring up around it. For a long time, the railway station at Vesijärvi Harbour was the second busiest station in Finland. Craftsmen, merchants, a few civil servants and a lot of industrial workers soon mixed in with the existing agricultural peasantry.
On 19 June 1877, almost the entire village was burned to the ground. However, the accident proved to be a stroke of luck for the development of the place, as it led to the authorities resuming their deliberations about establishing a town in Lahti. The village was granted market town rights in 1878 and an empire-style, grid town plan was approved, which included a large market square and wide boulevards. This grid plan still forms the basis of the city center. Most of the buildings were low wooden houses bordering the streets.
Lahti was founded during a period of severe economic recession. The Russian Empire was encumbered by the war against Turkey. The recession also slowed down the building of the township: land would not sell and often plots were not built on for some time. In its early years, the town with its meagre 200 inhabitants was too small to provide any kind of foundation for trade. At the end of the 1890s, Lahti’s Township Board increased its efforts to enable Lahti to be turned into a city. In spring 1904, the efforts finally bore fruit as the Senate approved of the application, although it was another eighteen months before Tsar Nicholas II finally gave his blessing and issued an ordinance for establishing the city of Lahti.
At the end of 1905, the area that now comprises Lahti