When did the incas begin to building their empire?

The Incas began building their empire in the early 15th century, around 1438, under the leadership of Pachacuti. They rapidly expanded their territory through military conquests and strategic alliances, eventually creating one of the largest empires in pre-Columbian America. By the time of the Spanish arrival in the 16th century, the Inca Empire covered vast regions of western South America.