Incas

The Incas, a South American native group, created the largest empire in the pre-Columbian Americas. The capital of the Incan Empire was at Cusco, in modern-day Peru. Between 1438 and 1533, the Incas conquered and assimilated most of western South America under their control, before falling to the Spanish conquistador Francisco Pizarro.
Until the 12th century, the Incas were a largely pastoral people, centered on the area of Cusco. Starting in 1438, they began a massive campaign of expansion, led by Sapa Inca Pachacuti-Cusi Yupanqui, the "earth shaker." It was Pachacuti who reorganized the Inca and their associated tribes into the empire later discovered by the Spanish.
There is no way to know exactly how many people were encompassed by the Incan Empire at its height, with estimates ranging from four to thirty-seven million. Surprisingly, the Incas lacked a written language, with their empire's communication consisting of ceramics and the spoken Quechua language. Their religious myths were passed down through oral traditions, until they were finally recorded by the earliest Spanish colonists. Central to their belief system was reincarnation. They also practiced human sacrifice. In 1529, Pizarro gained permission from Queen Isabella to conquer the Inca, leading an expedition in 1532 of 168 men south into Peru, leading to the destruction of the Inca's empire and culture.