Archaeology findings show that Sierra Leone has been inhabited for thousands of years. Traditional historiography has customarily presented it as a people by successive waves of invaders; but the language pattern suggests that the coastal Bulom (Sherbro), Temne, and Limba have been in continuous settled occupation for a long time, with sporadic immigration from inland Mende-speaking people including Vai, Loko and Mende. They organised themselves in small political units of independent kingdoms or chiefdoms, the powers of whose rulers were checked by councils. Secret societies, notably the Poro society also exercised political power as well as instructed initiates in the customs of the country.

Muslim traders brought Islam. Portuguese sailors, Alvaro Fernandez (1447) and Pedro Da Cintra (1462), were among the first European explorers to details their adventures along the coast of Sierra Leone. Located near present day Freetown, the Rokel estuary was established as an important source of fresh water for Sea Traders and explorers. Over the next 30 years, sea traders opened a bay for trading goods such as swords, kitchen and other household utensils in exchange for beeswax and fine ivory works. By the mid 1550’s, slaves replaced these items as the major commodity. Though the Portuguese were among the first in the region and their language formed the basis for trade, their influence had diminished by the 1650’s. English, French, Dutch and Danish interests in West Africa had grown. Trade was established through coastal African rulers who prohibited European traders from entering the interior. Rent and gifts were paid for gold, slaves, beeswax, ivory and cam wood.

British traders of the Royal African company established Forts along the coast for trading in 1672 but the British did not have monopoly on the area. Rival European nations attacked the Forts. Admiral de Ruyter is noted to having sacked Tasso Island in 1664 as a reaction to the maltreatment of Dutch traders. In 1728, Afro-Portuguese traders captured the New Royal African Company’s fort at Bunce Island.

Sierra Leone has a tropical climate, typified by warm temperatures and high humidity. Night time temperatures rarely drop below 24C and daytime temperatures reach 30C throughout the year. From October to March the weather is generally dry with many fine, hot, sunny days. From April to September, is the rainy season. The rainfall increases to a peak in July and August and then decreases until rain has almost ceased by November.

Sierra Leone's economy is predominantly agricultural, with most of its workers engaged in subsistence farming. The principal food crops are rice, cassava, corn, millet, and peanuts. The leading cash crops, most of which are exported, are palm kernels, palm oil, cocoa, and coffee. Poultry, cattle, sheep, and goats are raised. The fishing industry is also important.

The country has an important mining industry, which is largely controlled by foreign companies. The main minerals extracted are diamonds (the country's major source of hard currency), iron ore, gold, bauxite, and rutile. However, the mining industry, like other areas of the economy, was severely affected by civil strife. The country's few manufactures include refined petroleum and basic consumer goods. Sierra Leone has limited rail and highway networks, which mostly serve the central and western parts of the country. Freetown has excellent port facilities; smaller ports are located at Bonthe (on Sherbro Island) and Pepel (near Freetown).

The cost of Sierra Leone's imports is higher than its earnings from exports. The principal imports are machinery, manufactured consumer goods, foodstuffs, transportation equipment, and fuels; the chief exports are diamonds and other minerals, cacao, coffee, and fish. Diamond smuggling has been a problem since the 1960s, and during the civil war much of the diamond-mining area fell into the hands of rebel groups. Sierra Leone's leading trade partners are the European Union countries, the United States, and Côte d'Ivoire.