The Inca civilization had a highly organized agricultural system using terraces to grow crops like corn, potatoes, and quinoa. They stored surplus food by freeze drying it. Llamas were used as pack animals and for their wool, which was made into clothing. The Inca had specialized jobs and large cities made of stone with indoor plumbing. Their government was headed by the Sapa Inca, who was viewed as a god. People paid taxes to support the empire. They had an elaborate road system and traded throughout the empire without a monetary system. Record keeping was done using knotted string records called quipus.