In the 17th century Xanten was (along with Cleves) inherited by the Margraviate of Brandenburg. Protestantism was placed on an equal footing with the Roman Catholic Church, as confirmed by the "Treaty of Xanten" on 12 November 1614. Thereupon a church was built at the "Großer Markt" (Great Marketplace), which was expanded with a spire in 1622. Nevertheless, at the beginning of the 20th century only 5% of the population were of Protestant denomination. By the beginning of the 21st century, the Protestant share of the population had increased to some 20%.