History of Guinea-Bissau. Much to my surprise, President Grant was involved in helping to settle the boundaries of the African nation of Guinea-Bissau.
From the site:
Portuguese conquest and consolidation of the interior did not begin until the latter half of the 19th century. Portugal lost part of Guinea to French West Africa, including the center of earlier Portuguese commercial interest, the Casamance River region. A dispute with Great Britain over the island of Bolama was settled in Portugal's favor with the involvement of U.S. President Ulysses S. Grant.