By 1449, how many people were in the empire under Montezuma I?

The correct figure for the population of the empire under Montezuma I around 1449 is approximately 15 million people. This estimate is based on historical records and research regarding the Aztec Empire's expansion and the population in its most prosperous period. Under Montezuma I, the empire grew significantly, consolidating various regions and peoples into a powerful and highly organized society.

The population estimate of 15 million reflects urbanization, agricultural advancements, and the empire's effective governance, which allowed for the maintenance of large cities and the sustenance of complex social and economic systems. The Aztec capital, Tenochtitlán, was among the largest cities in the world at the time, which would contribute to a high population density.

Overall, the figure illustrates the scale of the Aztec civilization during its height and highlights the impressive demographic achievements of the empire prior to the Spanish conquest.