How did corn growing contribute to the size and sophistication of native american civilizations?

The growing of corn enabled the native Americans to have a much more reliable food source that was produced in large quantities and they also had reserves for bad times. This allowed the populations to grow significantly, and also larger cities to be built and developed. It also contributed that the people in this part of the world to have more time to focus on other things, like sciences, astronomy, architecture, instead of just living day by day and be in a constant search of food.