According to both indigenous American and European accounts and documents, American civilizations at the time of European encounter had achieved many accomplishments. For instance, the Aztecs built one of the largest cities in the world, Tenochtitlan, the ancient site of Mexico City, with an estimated population of 200,000. American civilizations also displayed impressive accomplishments in astronomy and mathematics. The domestication of maize or corn required thousands of years of selective breeding.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): How big was the population of the Aztec cit of Tenochtitlan?
200,000