Between the city and the island, there is the São Sebastião channel with 30 kilometres in length, and variable width (2 km being the shortest crossing).

The city is famous for its beaches, which makes it a popular tourism destination, especially for people from the state of São Paulo.

The municipality was named after Saint Sebastian in honor of the day that the Américo Vespúcio expedition sailed through the channel between the city and Ilhabela – January 20, 1502.

When slavery was abolished, in 1888, and the railway linking São Paulo to the bigger Port of Santos was opened, the city's economy entered a period of crisis, and the population decreased.

While the city centre kept developing, workers migrating from other parts of Brazil built their houses near the Serra do Mar, establishing the neighborhood of Topolândia, which now is home to the lower-class families.

São Sebastião became a tourist destination in the late 1980s, when the Rodovia Rio-Santos (a section of the BR-101 that connects Santos to Rio de Janeiro) was completed.

Most of the lands were sold to countryside or paulistanas families who wished a house to spend the weekends and holidays on the coast.

[4] However, after a project by the government of the state of São Paulo called "Onda Limpa" (Clean Wave), the percentage of houses connected to sewage pipes went up to 94% as of January 2012.

[7] Another current threat to the city is the sea level rise, which may affect several beaches and buildings located close to the shore.

[8] In March 2012, the deputy mayor of São Sebastião, Wagner Teixeira (PV) was caught doing illegal fishing off the coast of the city, near Paredão Island, Alcatrezes Archipelago.

[9] He was on his private boat with five other men, and didn't stop until his engine ran out of gas, even with the coast guard on his tail with sirens on.

[9] The Port of São Sebastião will receive considerable investment in the next decade so that it increases its operation capacity in a long-term expansion project due to continue until 2035.

Viewed from north to south, the Toque-Toque Grande island comes first after Ilhabela, and is located in front of the beach of the same name.

Local grassroots efforts are underway to create an ecotourism educational center focusing on sustainable living.

[12] The Ilha Montão de Trigo lies 10 km (8.7 mi) south of the nearest beach (Barra do Una).

It is part of the annual Volta do Parcel, an open water swimming competition which starts at the beach, takes the athletes around the islet and finishes back at Juqueí.

[18] The Ilha do Maracujá (Passion Fruit Island) is a small islet located in front of the wild beach of Brava, between Juréia and Boracéia.

There are a number of bars and ice cream shops, a handicraft fair and a large recreational square, which includes the largest skatepark in Brazil, measuring 7,000 m2.

[23] The company is currently an operator of cell phones, fixed lines, internet (fiber optics/4G) and television (satellite and cable).

The highway is the most important road of the city, connecting it from north to south, and having a regular bus line running all through it.