Which European nation controlled most of the Congo River?

The Portuguese were among the first Europeans to begin to explore the regions around the Congo River in the late 1400s and to make contact with the indigenous people of the areas. It was not until the 1800s, however, that other European nations became interested in colonizing the area. By that time, the Portuguese had already established themselves in the area to the south of the Congo River, which is now known as Angola.