Montrouge is a commune in the southern Parisian suburbs, located 4.4 km (2.7 mi) from the centre of Paris, France. It is one of the most densely populated municipalities in Europe. After a long period of decline, the population has increased again in recent years. The name "Montrouge" means Red Mountain, the name of the community was first mentioned in monastery documents in 1194. Industrial development started in 1925 and soon, many printing factories were to be found in the town. Most of these have disappeared today. Since the early years of the twenty-first century, professional services and telecommunications have been the main business activities.