The article presents the results of the phonemic-graphemic analysis of the German charters from the Cracow city book, which were written down in the 14th century. Due to the analysis, it could be proved that the text contains the majority of the dialectal Early New High German features and the sound changes which are characteristic for the Silesian dialect, and which spread in Central, Eastern and Southeast Europe within the context of German Eastward Expansion. All the results of the exploration are supported with appropriate examples.