The Major Turning Point in US History Discussion

I’m trying to learn for my History class and I’m stuck. Can you help? Turning points are significant events in history which become catalysts for change. These changes, for example, can inspire legislation and war, cause victory or defeat, and lead to the evolution of national ideologies. Some turning points are more obvious than others and are referenced often in the study of history, while others may not be.  It is our continued analysis of historical events that determine these significant moments and how they have helped shape the culture of the United States. For your final assessment, you will be identifying, describing, and analyzing a major turning point in U.S. history between the years 1400 and 1865.