   Nicolaus Copernicus was born on 19 February 1473, the youngest of four children of Nicolaus Copernicus, Sr., a well-to-do merchant who had moved to Torun from Cracow, and Barbara Watzenrode, the daughter of a leading merchant family in Torun. The city, on the Vistula River, had been an important inland port in the Hanseatic League. However, fighting between the Order of the Teutonic Knights and the Prussian Union in alliance with the Kingdom of Poland ended in 1466, and West Prussia, which included Torun, was ceded to Poland, and Torun was declared a free city of the Polish kingdom. Thus the child of a German family was a subject of the Polish crown.