Peru is a country in western South America, officially known as the Republic of Peru. Ecuador and Colombia border it on the north, Brazil on the east, Bolivia on the southeast, Chile on the south, and the Pacific Ocean on the south and west. Peru is a megadiverse nation with ecosystems ranging from the arid plains of the Pacific coastal zone in the west to the Andes mountain peaks stretching from the north to the southeast of the country to the tropical Amazon Basin rainforest in the east with the Amazon river. Peru is the 19th largest nation in the world and the third largest in South America, with 1.28 million km2. Several ancient peoples lived in Peruvian territory. From the Norte Chico civilization, which began in 3500 BCE and is one of the five cradles of civilization, to the Inca Empire, the largest pre-Columbian state in the Americas, the territory that now includes Peru has one of the longest histories of civilization of any region, dating back to the 4th millennium BCE. In the 16th century, the Spanish Empire invaded the region and created a viceroyalty that included much of its South American territories, with Lima as its capital. In 1551, the National University of San Marcos in Lima became the first institution of higher learning in the Americas. Peru declared independence in 1821, and it was completed in 1824, following the international military campaigns of José de San Martn and Simón Bolvar, as well as the decisive battle of Ayacucho. The nation enjoyed relative economic and political stability in the years following, which ended shortly before the Pacific War with Chile. Peru experienced armed territorial disputes, coups, civil instability, and internal conflicts in the twentieth century, as well as periods of peace and economic growth. Alberto Fujimori was elected president of Peru in 1990, and his government is credited with stabilizing the economy and putting an end to the Shining Path insurgency, despite widespread accusations of human rights abuses and repression of political dissent. In 2000, Fujimori resigned as president and was charged with and imprisoned for human rights abuses. Fujimori's supporters, known as Fujimoristas, also caused political instability for any competing party in power even after the president's rule ended. After a corruption scandal became public, the last elected president, Pedro Pablo Kuczynski, resigned in March 2018 to prevent impeachment by a Fujimorista-dominated congress. Peru is a sovereign state that is divided into 25 regions and is governed by a parliamentary democratic republic. Peru is a developing nation with a high level of human growth, an upper middle income level, and a poverty rate of about 19 percent, ranking 82nd on the Human Development Index. With an annual growth rate of 5.5%, it is one of the region's most stable economies.