As part of the Kingdom of Prussia, "Cöslin" was heavily damaged by a fire in 1718, but was rebuilt in the following years. In 1764 on the Chełmska Hill, now located within the city limits, a Pole Jan Gelczewski founded a paper mill that supplied numerous city offices. The city was occupied by French troops in 1807 after the War of the Fourth Coalition. Following the Napoleonic wars, it became the capital of Fürstenthum District (county) and Regierungsbezirk Cöslin (government region) within the Province of Pomerania. The Fürstenthum District was dissolved on 1 September 1872 and replaced with the Cöslin District on December 13. Between 1829 and 1845, a road connecting Koszalin with Szczecin and Gdańsk was built. Part of this road, from Koszalin to the nearby town of Sianów, was built in 1833 by around one hundred former Polish insurgents.