Saint Martin is an island in the northeast Caribbean Sea, approximately 300 km (190 mi) east of Puerto Rico. The 87-square-kilometre (34 sq mi) island is divided roughly 60/40 between the French Republic (53 km2, 20 sq mi) and the Kingdom of the Netherlands (34 km2, 13 sq mi), but the two parts are roughly equal in population. The division dates to 1648. The southern Dutch part comprises Sint Maarten and is one of four constituent countries that form the Kingdom of the Netherlands. The northern French part comprises the Collectivity of Saint Martin and is an overseas collectivity of France. Only the French part of the island is part of the European Union.