Question: when were the urban sites of cahokia and chaco canyon in north america both abandoned

title: Cahokia
text: At the high point of its development , Cahokia was the largest urban center north of the great Mesoamerican cities in Mexico and Central America . Although it was home to only about 1,000 people before c. 1050 , its population grew rapidly after that date . According to a 2007 study in Quaternary Science Reviews , `` Between AD 1050 and 1100 , Cahokia 's population increased from between 1400 and 2800 people to between 10,200 and 15,300 people '' . an estimate that applies only to a 1.8 km2 high density central occupation area . Archaeologists estimate the city 's population at between 6,000 and 40,000 at its peak , with more people living in outlying farming villages that supplied the main urban center . In the early 21st century , new residential areas were found to the west of Cahokia as a result of archeological excavations , increasing estimates of area population . If the highest population estimates are correct , Cahokia was larger than any subsequent city in the United States until the 1780s , when Philadelphia 's population grew beyond 40,000 . Moreover , according to the same population estimates , the population of 13th Century Cahokia was equal to or larger than the population of 13th Century London .