Complex sentence: After the expiration of the annuity schedule laid out in the 1836 treaty, Native Americans stopped coming to Mackinac Island in large numbers and the Indian Dormitory ceased to be of service in its original function.
Split into simpler sentences: After the expiration of the annuity schedule laid out in the 1836 treaty, Native Americans stopped coming to Mackinac Island in large numbers. The Indian Dormitory ceased to be of service in its original function.