Part of the Kingdom of Prussia since 1701, the town was incorporated into the Province of East Prussia after its creation in 1773. It was heavily devastated during the Napoleonic Wars. It remained mostly a small hamlet in the largely rural area around it. Agriculture, fishing and the richness of the surrounding forests provided the sources of income for the local population. Just like all of Masuria the district was inhabited mainly by Poles, and town itself had majority Polish population in 1816 however in the 19th century their percentage began to decrease due to Germanisation, removal of the Polish language from schools and the pressure of the local German administration (from 86% in 1825 to 59% in 1890). The town became the county seat in 1818, with its first "Landrat" (country executive) being August von Lyśniewski. In 1871 Sensburg became part of the German Empire during the Prussian-led unification of Germany. In 1897 the town became connected to the railway system, which went from Bischofsburg (Biskupiec) to Rastenburg (Kętrzyn/Rastembork). In 1903 the city received a donation from Edward Pałasz to acquire its own forest, where it then built recreational facilities.