Luxembourg an independent state under the personal possession of William I of the Netherlands with a Prussian garrison to guard the city against another invasion from France. In 1839, following the turmoil of the Belgian Revolution, the purely Oil-speaking part of Luxembourg was ceded to Belgium and the Luxembourgish-speaking part (except the Arelerland, the area around Arlon) became what is the present state of Luxembourg. Luxembourg is a founding member of the European Union, OECD, United Nations, NATO, and Benelux. The city of Luxembourg, which is the country's capital and largest city, is the seat of several institutions and agencies of
Southern Netherlands Orange at the 1815 Congress of Vienna. The southeastern third of Luxembourg Province was made into the autonomous Grand Duchy of Luxembourg, because it was claimed by both the Netherlands and Prussia. In 1830 the predominantly Roman Catholic southern half became independent as the Kingdom of Belgium (the northern half being predominantly Calvinist). In 1839 the final border between the kingdom of the Netherlands and Belgium was determined and the eastern part of Limburg returned to the Netherlands as the province of Limburg. The autonomy of Luxembourg was recognised in 1839, but an instrument to that effect was not signed