Map of the Kingdom of Kongo at its greatest extent in the 17th century 

At its height, Kongo was the biggest state in Central Africa. It stretched from the Atlantic in the west to the Kwango River in the east, encompassing what today is northern Angola, part of DR Congo and part of Congo Brazzaville. 
More on Kongo: Under the Sign of the Cross: Religious conversion in early modern Central Africa

Map of the Kingdom of Kongo at its greatest extent in the 17th century 

At its height, Kongo was the biggest state in Central Africa. It stretched from the Atlantic in the west to the Kwango River in the east, encompassing what today is northern Angola, part of DR Congo and part of Congo Brazzaville. 

More on Kongo: Under the Sign of the Cross: Religious conversion in early modern Central Africa