Final answer:
Cahokia was the largest and most influential city in the Mississippian period. It contained over one hundred mounds, with Monk's Mound being the largest and most important. It served as the political and religious center of the city.
Step-by-step explanation:
The largest and most influential city in the Mississippian period was Cahokia, located near modern St. Louis, Missouri. At its peak around 1100 CE, Cahokia covered nearly four square miles and housed a population of as many as thirty thousand people. It contained over one hundred mounds, with the largest and most important being Monk's Mound, a ten-story high structure that served as the focal point of the city's political and religious activities.