It is 25 km (16 mi) north of its mouth, but is only separated from the Atlantic Ocean to its west by the Langue de Barbarie, a 300 m (980 ft) wide sand spit.

Part of the Sahel, a transitional desertic band that separates "[...] the dunes of the Sahara from the baobabs of the savanna",[7] Saint-Louis' landscape is characterized by occasional acacias and is disturbed by sand storms during the dry season.

The marshes are flood basins that form during the rainy season when the river overflows into the countryside, creating ponds and stretches of mangroves that attract birds like flamingos and pelicans.

[8] Among Saint-Louis' numerous natural sites are the National Park of the Langue de Barbarie, the National Park of the Birds of Djoudj, the Fauna Reserve of Gueumbeul, beaches like that of the Langue de Barbarie, the colonial waterworks at Makhana, the palace of Baron Roger [fr] at Richard-Toll, the Diama Dam, and various hunting lodges on the south side of the Senegal River.

This park, which is 20 square kilometres large, occupies the southern point of the Langue de Barbarie, the estuary of the Senegal river and part of the continent.

It hosts thousands of water birds like cormorants, brushes, pink flamingos, pelicans, herons and ducks each year.

Located at a dozen kilometers south of the city of Saint-Louis, this reserve has an area of 7 square kilometres and shelters birds and endangered species such as the dama gazelle, the Patas monkey and the African spurred tortoise.

[11] A Wolof settlement at what is now known as Guet Ndar dates from around 1450 and was a meeting and departure point for Muslim pilgrims traveling to Mecca in Arabia.

[6] Portuguese, Dutch, and English traders visited the area over the next two centuries but the first nearby colonial fortification was erected by the French in 1638 on Bocos Island, about 25 km (16 mi) away.

As in Gorée, a Franco-African Creole, or Métis, merchant community characterized by the famous "signares", or bourgeois women entrepreneurs, grew up in Saint-Louis during the 17th and 18th centuries.

They created a distinctive urban culture characterized by public displays of elegance, refined entertainment and popular festivities.

[16]: 115–6 Throughout the 19th century, the French periodically warred with the Emirate of Trarza and other Hassani tribal states, which disrupted the flow of gum.

His large-scale projects included the building of bridges, provisioning of fresh drinking water, and the construction of an overland telegraph line to Dakar.

Large French firms, many from the city of Bordeaux, took over the new commercial networks of the interior, marginalizing the Métis traders in the process.

The colonial institutions set up in the city in the 19th century, such as the Muslim Tribunal and the School for Chiefs' Sons, were to play important roles in the history of French Africa.

The loss of its past status meant less recognition and lack of interest from the colony's officials and, after Senegal's independence, from the Senegalese government.

[3] In June 2008, Alioune Badiane of the United Nations' UN-Habitat agency designated Saint-Louis as "the city most threatened by rising sea levels in the whole of Africa", citing climate change and a failed 2004 river and tidal canal project as the cause.

[21] Saint Louis has economically declined since the transfer of the capital to Dakar, but has remained an important tourist and trading center.

Its other economic activities are fishing, irrigated alluvial agriculture, pastoral farming, trading and exportation of peanut skins.

The Wolofs and Lebous who are the main inhabitants of Saint-Louis are mostly fishermen that live in fishing communities like Guet-Ndar on the Langue de Barbarie.

The heritage of the signares lives on in the city's many festivals and its cultivated sense of public display, and it is helping Saint-Louis emerge from decades of neglect.

After World War II, visiting U.S. GIs popularized jazz bands and by the 1950s local groups had adopted a "Cuban" sound.

The annual reggata, or pirogue race organized by teams of fishermen from Guet-Ndar, takes place on the "little branch" of the river, between Ndar Island and the Langue de Barbarie.

The Magal of the Niari Rakas, a yearly commemoration of Cheikh Ahmadou Bamba Mbacké's (the founder of Mouridism) two prayers in the Governor's Palace in 1895, is the city's largest religious gathering.

The Island of Saint-Louis is inscribed on the World Heritage list on the basis of criteria II and IV: Criterion II The historic town of Saint-Louis exhibits an important exchange of values and influences on the development of education and culture, architecture, craftsmanship, and services in a large part of West Africa.