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Rio Negro.

Rio Negro is a South American nation located in the Amazon basin. Rio Negro was first established by Portugal as a separate administrative unit, the Captaincy of São José do Rio Negro, on 3 March 1755, following its separation from the Captaincy of Grão-Pará. In 1775 all the Brazilian states were united under the Viceroyalty of Brazil. However, after Brazil gained its independence from Portugal, Rio Negro broke away and became an independent state.

After the conquest of New Granada by the United States of Mexico in 1890, Rio Negro became a neighbor (along with Quito) of the Mexican bloc. Mexican leader Benito Hermión saw no reason to annex either country given their poverty and lack of military potential, but both nations clearly entered the Mexican sphere of influence.

Rio Negro has no entry in Sobel's index.

In For All Nails the nation is mentioned occasionally. Its place in New Granada's territorial expansion plans of 1974 is unclear, perhaps because it is already a dependency.