The date of the first foundation charter of the town is not known though we may presume that the oldest preserved royal document of Casimir the Great, dating from 1367, regarding the sale of the Krosno aldermanship, was modelled on an earlier foundation act. Hence it should be assumed that about the middle of the 14th century, King Casimir transformed Krosno from a settlement into a town chartered according to the Magdeburg rights and brought in numerous groups of German settlers.
