During the 19th Century rubber was produced in the Congo Free State amidst horrendous conditions of forced labor. The Congo Free State was under the control of which colonial power?

The Congo Free State (French: État indépendant du Congo, lit. "Independent State of the Congo") was a large state in Central Africa from 1885 to 1908, which was in personal union with the Kingdom of Belgium under Leopold II. Leopold was able to procure the region by convincing the European community that he was involved in humanitarian and philanthropic work and would not tax trade.[2] Via the International Association of the Congo he was able to lay claim to most of the Congo basin. On May 29, 1885, the king named his new colony the Congo Free State. The state would eventually include an area about the size of the present Democratic Republic of the Congo.

Leopold's reign in the Congo eventually earned infamy due to the increasing mistreatment of the indigenous peoples. Leopold extracted ivory, rubber, and minerals in the upper Congo basin for sale on the world market, even though his nominal purpose in the region was to uplift the local people and develop the area. Under Leopold II's administration, the Congo Free State became one of the greatest international scandals of the early-20th century. The report of the British Consul Roger Casement led to the arrest and punishment of white officials who had been responsible for killings during a rubber-collecting expedition in 1903.