According to several sources, the first historic reference to Słupsk comes from the year 1015 when the king of Poland Boleslaus I the Brave took over the town, incorporating it into the Polish state. In the 12th century, the town became one of the most important castellanies in Pomerania alongside Gdańsk and Świecie. However, several historians stated that the first mention was in two documents dating to 1227, signed by the Pomeranian dukes Wartislaw III and Barnim I and their mothers, confirming the establishment of an abbey in 1224 and donating estates, among them a village "in Stolp minore" or "in parvo Ztolp", respectively, to that abbey. Another document dated to 1180, which mentions a "castellania Slupensis" and would thus be the oldest surviving record, has been identified as a late 13th-century or 14th-century duplicate.