City rights were granted in 1306. Lenzburg was conquered by Bern in 1415, along with the western part of what is now Aargau. Bern did not take away its city rights. In 1433, the city of Bern bought the castle and used it to govern the area from 1444 to 1798. A major fire ruined the town in 1491. Only fifteen houses were not destroyed. The reformation was carried out at the same time with the rest of the region in 1528. The economy started to move slowly from a farming economy to a more industrial one in the 16th century. A textile factory was founded in 1732.