Beginning in the late 1870s the territory was colonized by Leopold II, king of the Belgians. Leopold believed that Belgium needed colonies to ensure its prosperity, and sensing that the Belgians would not support colonial ventures, he privately set about establishing a colonial empire. Between 1874 and 1877, Henry M. Stanley made a journey across central Africa during which he found the course of the Congo River. Intrigued by Stanley's findings (especially that the region had considerable economic potential), Leopold engaged him in 1878 to establish the king's authority in the Congo basin. Between 1879 and 1884, Stanley founded a number of stations along the middle Congo River and signed treaties with several African rulers purportedly giving the king sovereignty in their areas.
At the Conference of Berlin (1884–85) the European powers recognized Leopold's claim to the Congo basin, and in 1885 the king announced the establishment of the Congo Free State, headed by himself. The announced boundaries were roughly the same as those of present-day Congo, but it was not until the mid-1890s that Leopold's control was established in most parts of the state.
Because he did not have sufficient funds to develop the Congo, Leopold sought and received loans from the Belgian parliament in 1889 and 1895, in return for which Belgium was given the right to annex the Congo in 1901. At the same time Leopold declared all unoccupied land (including cropland lying fallow) to be owned by the state, thereby gaining control of the lucrative trade in rubber and ivory. Much of the land was given to concessionaire companies.
The Belgian parliament did not exercise its right to annex the Congo in 1901, but reports starting in 1904 about the brutal treatment of Africans there (especially those forced to collect rubber for concessionaire companies) led to a popular campaign for Belgium to take over the state from Leopold. After exhaustive parliamentary debates, in 1908 Belgium annexed the Congo.
Annexation to Belgium was accomplished by means of the Treaty of November 15, 1908, approved by the Belgian Parliament in August and by the King in October of the following year. The colony was administered by a governor-general and in Brussels, there was a colonial minister. The colony was divided into 15 administrative districts. The colonial budget was voted annually by the Belgian Parliament.
When the Belgian Government took over the Administration from King Leopold II, the situation in the Congo improved dramatically. Primary and high schools were built as well as hospitals, and many Congolese had access to them. Even the ethnic languages were taught at school, a rare occurrence in colonial education. The Administration continued with the economic reforms with the construction of railways, ports, roads, mines, plantations, industrial areas, etc.
Political administration fell under the total and direct control of the mother country; there were no democratic institutions. The Belgian government controlled the country, but day-to-day operations were carried out by the governor general who was appointed by the government. There was also a kind of "Apartheid", as there were curfews for natives and other such restrictions were commonplace.
In 1952, Governor-General wrote to the Secretary of Colonies, saying that that if nothing was done to ameliorate the situation in the Congo, Belgium would lose its richest colony. He wanted to give the native people more civil rights, even suffrage. But the Belgian government was against this proposal. In Belgium, some members of Parliament wanted to incorporate the Congo into the Belgian Kingdom. Native Congolese people would thus be Belgian citizens, and would therefore have full political rights. However, Belgium was not very interested in its colony, as the government never had a strategic long-term vision about the Congo. Nevertheless, there were some internal political changes, but these were complicated by ethnic rivalries among the native population. It must be noted, that even in the 1950s forced labour still continued in Congo, and that the life expectancy was less than forty years.
The Republic of the Congo became independent on 30 June 1960.

Congo Free State stamps:

1: 1886 set: king Leopold II
2: 1887 set: king Leopold II
3-8: 1894 set: landscapes
9, 10: 1895 set (new colors)
11, 12: 1896 set
13-17: 1900 set (new colors)