Saint-Louis (săN-lwē) [key], city (1988 pop. 160,689), NW Senegal, a port at the mouth of the Senegal River. The terminus of a railroad from Dakar, it is a fishing, trade, and export center for peanuts, hides, and skins. The oldest French colonial settlement in Africa, Saint-Louis was founded (1638) on an island in the river as a trade base. In 1659 a French fort was built there. Except for brief periods (1758–79; 1809–15) of British rule, it was the capital of all French possessions in W Africa and capital of French West Africa from its inception (1895) until 1902. Saint-Louis was subsequently (1902–58) capital of both Senegal and Mauritania. It has declined since independence but remains an important administrative, tourist, and trading center.