The seat of the government of the Congo Free State was at this time the port town of Boma, which lies on the Congo River around 100 km from Muanda, where the river meets the Atlantic Ocean. Boma served as the capital of the Congo Free State and Belgian Congo from 1886 until 1926, when the capital was moved to Leopoldville (since renamed Kinshasa).
In the original manuscript Conrad had offered a much fuller description of Boma:
We went up some twenty miles and anchored off the seat of the government. I had heard enough in Europe about its advanced state of civilization: the papers, nay the very paper vendors in the sepulchral city were boasting about the steam tramway and the hotel – especially the hotel. I beheld the wonder. It was like a symbol at the gate. It stood alone, a grey high cube of iron with two tiers of galleries outside towering above one of those ruinous-looking foreshores you come upon at home in out-of-the-way places where refuse is thrown out. To make the resemblance complete it wanted only a drooping post bearing a board with the legend: rubbish shot here, and the symbol would have had the clearness of the naked truth …
The passage was excised presumably because Conrad did not want to include any suggestion of economic or structural development in the colony that could be used as mitigation for the various crimes of the colonial enterprise.