The German ethnicity developed among early Germanic peoples of Central Europe in the Early Middle Ages. The Kingdom of Germany emerged from the eastern remains of the Carolingian Empire in the 9th century, and formed the core of the Holy Roman Empire. In subsequent centuries the German population grew considerably and a substantial number of Germans migrated to Eastern and Northern Europe. Following the Reformation in the 16th century, the German lands became divided into Roman Catholic and Protestant states. The 19th century saw the dismemberment of the Holy Roman Empire and the growth of German nationalism, with the state of Prussia incorporating most of the Germans into the German Empire, while a substantial number of Germans also inhabited Austria-Hungary. During this time a large number of Germans emigrated to the New World, particularly to the United States, Canada and Brazil. The Russian Empire also contained a substantial German population.