thousand years ago the territory now known as Liberia was occupied by the Mandé, Kru and Atlantic Mel-speaking peoples from the north and east and in the mid-15th Century the coastal towns were conducting a flourishing slave trade with European merchants. Modern Liberia (derived from the Latin liber or freedom) was the creation of the American Colonization Society (ACS) founded in 1816 to encourage the return of freed slaves to Africa, similar to a program organized by the British in Sierra Leone. Over a period of 40 years some 12,000 slaves were voluntarily resettled. The original constitution denied indigenous Liberians equal rights with these American emigrants and their descendants. With modest assistance from the US government, Monrovia, named after President James Monroe, and other settlements such as Robertsport, Buchanan, Greenville and Harper, were established. On 26 July 1847 Liberia declared itself a sovereign and independent republic. Though the government at Monrovia claimed to rule all the people along the Liberian coast and for some distance inland, effective administration was limited to the coast where the settlers and their descendants lived. It was only since 1920 that real progress was made towards opening up the interior with the help of a 43 mile (69 km) railroad from Monrovia to the Bomi Hills. American influence remained strong. The US dollar was then, and still is, the preferred currency. Firestone rubber company was the first major investor. President William Tubman, a descendant of the African American settlers, served seven consecutive terms and his successor, William Tolbert, ruled from 1971 to 1980, when he was killed by Master Sergeant Samuel Doe, self-styled leader of the National Democratic Party of Liberia (NDPL). A devastating civil war raged from 1989 until 1996. In accordance with the Abuja Accord the warring Liberian factions agreed to participate in elections during July 1997. Charles Taylor's National Patriotic Front of Liberia won in an election declared free and fair by foreign observers, including former US President Jimmy Carter. Soon faced with renewed insurgency by, among others, Liberians United for Reconciliation and Democracy (LURD), Taylor resorted to force and involved himself in destabilizing neighboring Sierra Leone and Guinea. In August 2003, Taylor was forced to go into exile in Nigeria and was replaced by Deputy President Moses Blah who in turn stepped down in favor of entrepreneur Gyude Bryant who promised free elections. The presence of a West African peacekeeping force helped maintain some measure of stability until the November 2005 presidential elections. Harvard graduate and former World Bank official, Dr. Ellen Johnson-Sirleaf, defeated world soccer star George Weah to become Africa's first female head of state. Weah's Congress for Democratic Change (CDC) captured a majority in the legislature with Johnson-Sirleaf's United Party forming the main opposition.