Most Mesoamerican and South American cultures practiced human sacrifice as part of their religious rituals, in order to satisfy or appease their gods. However, the specific answer depends on the civilization you are talking about.
The Maya believed that cenotes were portals to the underworld, so humans were tossed down cenotes in order to please the water god Chaac. The Aztecs, on the other hand, practiced human sacrifice on a much larger scale as an offering to Huitzilopochtli to restore the blood lost in his daily war. The Inca also performed ritual sacrifice during and after important events, particularly child and teenage sacrifice.
