 The former Polish Pomerelian lands beyond the Vistula River together with Malbork and Chełmno Land formed the Province of West Prussia with its capital at Marienwerder (Kwidzyn).The Polish Partition Sejm ratified the cession on 30 September 1773, whereafter Frederick officially went on to call himself a King "of" Prussia.The former Ducal Prussian districts of Eylau (Iława), Marienwerder, Riesenburg (Prabuty) and Schönberg (Szymbark) passed to West Prussia.