The Ancient civilizations of the Maya, Aztec and Inca flourished in Central and South America in the centuries before European colonists came to the region in the 15th and 16th Centuries.  But further North, in what is now the United States, there were also large indigenous settlements.  Cahokia, in the present state of Illinois, was the largest.  At its peak, sometime around the 12th Century, Cahokia was home to nearly 20,000 people.  VOA’s Arash Arabasadi has more.