Archaeological finds show that Sierra Leone has been inhabited continuously for at least 2,500 years, populated by successive movements from other parts of Africa. Sierra Leone by the 9th century, and by AD 1000 agriculture was being practiced by coastal tribes. Sierra Leone's dense tropical rainforest largely protected it from the influence of any precolonial African empires and Islamic colonization, which were unable to penetrate through it until the 18th century.
In 1462, a Portuguese explorer by the name of Pedro da Cintra mapped the hills surrounding what is now Freetown Harbour, naming the shaped formation “Serra de Leão” (Portuguese for Lion Mountains). Its Italian rendering is Sierra Leone, which became the country's name. Soon after Portuguese traders arrived at the harbour and by 1495 a fort that acted as a trading post had been built. The Portuguese were later joined by the Dutch and French; all of them using Sierra Leone as a trading point for slaves. In 1562 the English joined the trade in slaves when Sir John Hawkins bought 300 slaves.
In 1787, a plan was implemented to settle some of London's Black Poor in Sierra Leone in what was called the “Province of Freedom”. A number of Black Poor and White women arrived off the coast of Sierra Leone on May 15, 1787, accompanied by some English tradesmen. This was organized by the St. George's Bay Company, composed of British philanthropists who preferred it as a solution to continuing to financially support them in London. Many of the Black poor were African Americans, who had been promised their freedom for joining the British Army during the American Revolution, but also included other African and Asian inhabitants of London.
Disease and hostility from the indigenous people nearly eliminated the first group of colonists. Through intervention by Thomas Peters, the Sierra Leone Company was established to relocate another group of former slaves, this time nearly 1,200 Black Nova Scotian's, most of whom had escaped slavery in the United States. Given the most barren land in Nova Scotia, many had died from the harsh winters there. They established a settlement at Freetown in 1792 led by Thomas Peters. This group was later joined by other groups of freed slaves and became the first Afro-American haven for ex-slaves.
Though the English abolitionist Granville Sharp originally planned Sierra Leone as a utopian community, the directors of the Sierra Leone Company refused to allow the settlers to take freehold of the land. Knowing how Highland Clearances benefited Scottish landlords but not tenants, the settlers revolted in 1799. The revolt was only put down by the arrival of over 500 Jamaican Maroons, who also arrived via Nova Scotia.
Thousands of slaves that were returned to or liberated in Freetown chose to remain in Sierra Leone. These returned Africans were from many areas of Africa, but principally the west coast. They joined the previous settlers and together became known as Creole or Krio people. Cut off from their homes and traditions, they assimilated some aspects of British styles of inhabitants and built a flourishing trade of flowers and beads on the West African coast. The lingua franca of the colony was Krio, a creole language rooted in 18th century African American English, which quickly spread across the region as a common language of trade and Christian mission. British and American abolitionist movements envisioned Freetown as embodying the possibilities of a post-slave trade Africa.
On April 27, 1961, Sir Milton Margai led Sierra Leone to Independence from the United Kingdom. He was the country's first Prime Minister. He was a veteran medical doctor who had been appointed Chief Minister after the Colonial Legislative Council and the Protectorate Assembly were unified in 1951. His political party, the Sierra Leone People's Party (SLPP), won by large margins in the nation's first general election under universal adult suffrage in May 1962. It also won majority of seat in parliament. Upon his death in 1964, his brother, Sir Albert Margai succeeded him as prime minister. Sir Albert was highly criticized during his three-year rule as prime minister. He tried to establish a one-party but met fierce resistance from the opposition All People's Congress (APC) and he ultimately abandoned the idea.
In a closely contested general elections in March 1967, Sierra Leone Governor General Henry Josiah Lightfoot Boston declared the new Prime Minister to be Siaka Stevens, candidate of the All People's Congress (APC) and Mayor of Freetown. Hours after taking office, Prime Minister Stevens was ousted in a bloodless coup led by Brigadier David Lansana, the Commander of the Armed Forces however, a group of senior military officers overrode this action by seizing control of the government on March 23, 1968, arresting Brigadier Lansana and suspending the constitution. The group constituted itself as the National Reformation Council (NRC) with Brigadier Andrew Juxon-Smith as its chairman. In April 1968, the NRC was overthrown by a group of military officers who called themselves the Anti-Corruption Revolutionary Movement (ACRM), led by Brigadier John Amadu Bangura. The ACRM imprisoned senior NRC members, restored the constitution and reinstated Siaka Stevens as Prime Minister.
The return to civilian rule led to by-elections beginning in fall 1968 and the appointment of an all-APC cabinet. Calm was not completely restored. In November 1968, Siaka Stevens declared a state of emergency after provincial disturbances. In March 1971 the government survived an unsuccessful military coup and in July 1974 it uncovered an alleged military coup plot. The leaders of both plots were tried and executed. In 1977, student demonstrations against the government disrupted Sierra Leone politics.
On April 19, 1971, Parliament declared Sierra Leone a Republic. Siaka Stevens, then prime minister, became the nation's first president, and in March 1976 he was elected without opposition for a second five-year term as president. In 1978, Parliament approved a new constitution making the country a one-party stat. In the 1978 referendum the APC was made the only legal political party in Sierra Leone.
President Sir Siaka Stevens retired in November, 1985 after being President for 14 years, but continued to be chairman of the APC. The APC named a new presidential candidate to succeed Stevens. He was Major General Joseph Saidu Momh, the commander of the Republic of Sierra Leone Armed Forces, and Stevens' own choice to succeed him. Joseph Saidu Momoh was elected President in a one-party referendum on November 28, 1985.
In October 1990, President Momoh set up a constitutional review commission to review the 1978 one-party constitution. Based on the commission recommendations a constitution re-establishing a multi-party system was approved by Parliament; becomming effective on October 1, 1991.
Civil war broke out, under the command of former Sierra Leonean army corporal Foday Sankoh. Who launched his first attack in villages in Kailahun District in eastern Sierra Leone on March 23, 1991. The government of Sierra Leone, overwhelmed by a crumbling economy and corruption, was unable to put up significant resistance. Within a month of entering Sierra Leone Reitred Coporal Sankoh Revolutinary United Front controlled much of the Eastern Province.
On April 29, 1992, a group of young soldiers apparently frustrated by the government's failure to deal with rebels, launched a military coup which sent president Momoh into exile in Guinea . They established the National Provisional Ruling Council (NPRC) with Yahya Kanu as its chairman. But Kanu was assassinated by fellow NPRC members, who accused him of trying to negotiate with the toppled APC administration. On May 4, 1992,Captain Valentine Strasser took over as chairman of the NPRC and Head of State of Sierra Leone.
In January 1996, after nearly four years in power, Strasser was ousted in a coup by fellow NPRC members led by his deputy Maada Bio. Bio reinstated the Constitution and called for general elections. In the second round of presidential elections in early 1996, Ahmed Tejan Kabbah, candidate of the Sierra Leone People's Party (SLPP) defeated John Karefa-Smart of the United National People's Party (UNPP)
In 1996, Johnny Paul Koroma was allegedly involved in an attempt to overthrow the government of President Kabbah. He was arrested, tried, convicted, and imprisoned at Maxium Prison in Freetown. But some top ranking Army officers were unhappy with this decision, and on May 25, 1997, a group of soldiers who called themselves the Armed Forces Revolutionary Council (AFRC) overthrew President Kabbah's government. The AFRC released released Jonny Paul Koroma from prison and installed him as their chairman and Head of State of the country. After 10 months in office, the junta was ousted by the Nigeria-led ECOMOG forces, and the democratically elected government of President Kabbah was reinstated in March 1998.
In October, the United Nations agreed to send Peacekeepers to help restore order and disarm the rebels. By January 2002, the war was declared over. In May, President Kabbah was reelected.
In August 2007, Sierra Leone held presidential and parliamentary elections. However, no presidential candidate won a majority of votes. A runoff election was held in September, and Ernest Bai Koroma was elected president of the Republic of Sierra Leone