Santiago is located between the islands of Maio and Fogo and is one of the Sotavento. It was the first of the islands to be settled, the town of Cidade Velha being founded as Ribeira Grande in 1462. It is also home to the nation's capital city of Praia and to one of the islands’ four international airports, Praia International Airport, 3 kilometres from the capital.
In the 19th century it was called St. Jago.
During the Prehistoric era, around 22 to 21 million years ago, the seamount was formed, 4 to 3 million years ago, the island with its crater now known as Pico da Antónia was formed, its length was about 15 kilometres (9.3 miles), about 2 to 3 million years ago, another island with its crater at present day Serra da Malagueta was formed, its seamount was formed around 20 to 19 million years ago, its length was about 10 kilometres (6.2 miles), about 2 to 1 million years ago, the two islands merged into a larger island. In about 73,000 BC, the eastern portion of the island of Fogo collapsed into the ocean and brought a 170-metre-high (560 ft) megatsunami that flooded the western part of the island. During the Ice Age, the island was larger than 1,050 square kilometres (410 square miles) and approximately 80 kilometres (50 miles) wide.
The island was discovered by António da Noli in around 1460 who built a garrison in Cidade Velha which was then known as Ribeira Grande. Transcontinental slavery made Cidade Velha the second richest city in the Portuguese realm. Later, Portugal faced competition by the English, Dutch, French and Spanish who gradually took over the slave trade. The island was captured by Francis Drake, as a result, Fort Real de São Filipe, Cape Verde's first fortress was built and was finished in 1590. In 1712, the capital no longer served Cidade Velha which was attacked by French pirates led by Jacques Cassard as part of the Cassard expedition and was moved to the Praia plateau, Praia was not officially capital status until 1770. The island population were disadvantaged by the Portuguese colonial system and supported Amílcar Cabral and the African Party for the Independence of Guinea and Cape Verde and the independence of 1975. Santiago several times hosted conferences on Creole culture.
Santiago is the largest island of Cape Verde, with an area of 991 square kilometres (383 square miles). The island is mountainous, although slightly flatter in the southeast. In the area of Cidade Velha and west of Salineiro consists of a plateau that has very few hills and a lot of ravines, several of them deep. As does with many other islands in the country, within a kilometer or two within the island has the area inside the ocean that is 1 kilometer deep, 5 kilometers further is 2 kilometers deep and as far as ten kilometers away is the ocean floor which is about 3500 meters deep. The wetter climate of the interior and the eastern coast contrasts with the drier one in the south/southwest coast. Praia, located in the southeast coast, is the largest city on the island, and also the largest city and capital of the country. Other towns on the island include Cidade Velha, 15 kilometres (9.3 miles) west of Praia, Cape Verde's first capital; Assomada, 60 kilometres (37 miles) north and Tarrafal in the northern part of the island 75 kilometres (47 miles) from the capital. The island has the most number of villages and settlements in Cape Verde.
The tallest summit is Pico da Antónia which is located west of Picos, the second is Serra da Malagueta which is halfway between Assomada and Tarrafal. Other mountain ranges include Órgãos which dominate a part of the municipality including north of João Teves, Monte Vacas which dominate between Cidade Velha and São Domingos and Serra da Malagueta which dominates the north of the island. Pico da António and Serra Malagueta are its National Parks located on the island, they were created in 2003. The island are one of five that have one or more islands, one is Ilhéu de Santa Maria which is near Praia and the others are some rocky islets located near Ponta Moreia.
The length of the shoreline is around 120 km long making it the longest in the archipelago and much of it are surrounded by short and tall cliffs, many of the taller ones are on the west side. Many of the cliffs were formed from the massive Fogo eruption of 73,000 years ago in the west and most probably in other parts of the island including smaller ones in the east, it is recorded in its boulders that are seen today. The surrounding bays include Baía de Mosquito which is in the southwest and has one of the tallest cliffs on any island in the North Atlantic, Praia Harbor near Praia in the southeast and Tarrafal Bay to the northwest. The longest river is the Poilão Stream which flows in the southern interior other streams include Ribeira Grande de Santiago, Ribeira Grande do Norte de Santiago which empties in Chão Bom. The remainder of the island especially in the east has several small bays, the notable ones are the one in Calheta de São Miguel, the one near Pedra Badejo and Praia Formosa. The southernmost point is Praia Temerosa, the northernmost is Ponta Moreia and the easternmost is Ponta do Lobo located near Vale da Custa. Beaches on the island includes Praia Baixo, Praia Formosa, Tarrafal, Prainha near Praia, Cidade Velha, Pedra Badejo and Calheta de São Miguel and smaller ones including Chão Bom, Rincão, Ribeira da Barca, it is one of three islands that contains only small beaches. The island has no lagoons but has five reservoirs damming five artificial lakes including Poilão, Faveta, Figueira Gordo, Salineiro and Saquinho, some of these are dry during dry months.
The Cape Verde islands are a very degradated area. Due to their proximity to the Sahara, most of the Cape Verde islands are dry, but on islands with high mountains and farther away from the coast, by orography, the humidity is much higher, giving a rainforest habitat, very degraded by the strong human presence. Northeastern slopes of high mountains often receive a lot of rain and Southwest slopes not. These umbria areas are identified with cool and moisture. Some islands, as Santiago with steep mountains, are covered with vegetation where the dense moisture condense and soak the plants, rocks, soil, logs, moss etc.
Cloud forests developed about mountains, where the dense moisture from the sea or ocean, is precipitated by the action of the relief. Opposing the terrain to a front of warm, moist air mass, it forces to increase the height above sea level of that body wet and warm air mass, which cools and decreases the dew point, causing it to condense part of the moisture that falls as rain or fog, creating a habitat especially cool, saturated with moisture in the air and soil.
Almost all of the island are surrounded by the Cape Verde Rise, many areas are 1,000 meters deep, 10 km away from the island and 15-20 km are 2,000 meters deep and are being the limits of the seamount. East of Ponta do Lobo in a small area between Santiago and Maio, the deepest portion is over 1,000 meters deep.
As of 1830, Santiago's population was estimated at 24,000. Santiago has always been the most populous island in Cape Verde. The island population has doubled since the independence of Cape Verde in 1975. The 2010 census population of the island was 272,312.
The island has the longest road and street networks in the country. The total length of the main roads is 679.63 kilometres (422.30 miles), of which 363.23 kilometres (225.70 miles) are national and 313.40 kilometres (194.74 miles) are regional. The main highway is the one connecting Praia and Tarrafal via Assomada and another via Pedra Badejo and Calheta
The majority of the island's roads along with Cape Verdean roads are paved with cobblestones cut from local basalt. Recent international aid has allowed the asphalting of many roads, on the island including all of the highway between Praia and Tarrafal, all of the highway between Praia and Cidade Velha, and all of the highway between Praia, Pedra Badejo, and Calheta de São Miguel on Santiago, much of the paved roads are on the island.
The main port of the island is Praia (once used as a city name as Porto Praia). Tarrafal, Cidade Velha, Ribeira da Barca, Chão Bom, Pedra Badejo, Praia Formosa and Calheta de São Miguel are used as fishing ports.
Several towns and cities are served with aluguer buses common throughout Cape Verde. Praia has Cape Verde's only mass transit system. The system are run by Maura Company, newer ones are run by Sol Atlântico,.
Taxis are common in Praia and Assomada. Taxis with a base in Praia are painted beige, while taxis with a base in Assomada are painted white.
The main industries are agriculture, tourism, fishing and others, and leastly manufacturing. Main agricultural products are corn, sugar cane, banana, coffee and mangoes. The manufacturing and the business sector dominates in the capital of Praia along with the political sector. Most of the factories are also located in the capital.
Several media serves the island. The island are home to the country's television and radio station RTC, Record Cabo Verde and RTI. Regional stations includes [praiafm.biz Praia FM] and Radio Praia.
Institutions includes the National Library of Cape Verde, the country's only private university, the Jean Piaget University of Cape Verde and two universities, the University of Cape Verde, first opened in November 2006 and the University of Santiago Island with its campuses in Praia and Assomada. Also there is Cape Verde's first school named Escola Grande and the first lyceum, both located in Praia. In the south of Praia near Ponta Temerosa is the seminary of São José first opened in 1957.
Several endangered species are on the island. There are 38 species of endangered flora as of 2015 including Artemisia gorgonum, Campanula bravensis, Campanula jacobaea, Conyza feae, Conyza pannosa, Echium hypertropicum, Euphorbia tuckeyana, Lavandula rotundifolia, Limonium lobinii, Micromeria forbesii, Sarcostemma daltonii, Sonchus daltonii, Umbilicus schmidtii, notably founded in areas including Pico da Antónia, Serra Malagueta, the interior and Monte Graciosa and the island's north tip. Endangered fauna includesVerbascum capitis-viridis and fauna including birds such as Iago sparrow (or Cape Verdean sparrow) and Cape Verde warbler, skinks and geckos such as Chioninia spinalis, Chioninia stangeri, Chioninia vaillantii, Hemidactylus brookii angulatus,, Tarentola darwini (Darwin's gecko) and Tarentola rudis, the spider Koinothrix pequenops and Hottentotta caboverdensis, the only scorpion on the island and the archipelago. Surrounding the island have some fishes and snail furs. Iago sparrow and Darwin's gecko were first described on the island as well as a fish Diplodus prayensis (rarely as praiensis).
Along with the entire archipelago, all of its reptiles and insects as well as plants came on what was a possible clue, rafting on trees, probably from the banks of the mainland rivers of Senegal or large rivers from around modern day Guinea-Bissau or Guinea during the times when the salinity of the ocean was low.
After the Portuguese discovery, from the 16th century, non-indigenous plants and mammals were brought to parts of the island especially monkeys and farm animals.
In politics, Santiago is the only island that are divided into two constituencies, north and south, the south includes the three municipalities which include the capital, as of the 2011 election, it had 14 seats in the north with 8 PAICV seats and 6 MpD seats and 19 seats in the south with about 11 MpD seats. After the 2016 elections, the Mpd took the majority of the seats of the two zones, 60% in the north and 70% in the south.
The island are divided into two zones, the North and the South Zones and has football (soccer), basketball, volleyball, track and field, futsal and athletics competitions. Until 2003, the island had one island championships, the Santiago Island Championships. The unified island league would continue into 2007 featuring only a single match featuring the champions of the north and the south.
Santiago possesses the most major sports complexes in the country, they include Estádio da Várzea in Praia, Cumbem in Assomada, Mangue in Tarrafal, one in Pedra Badejo and Estádio da Calheta in Calheta de São Miguel.