Simplify the following text for a Grade 10 native English-speaking person.
Original: The Great Fire of New York was a devastating fire that burned through the night of September 21 , 1776 on the west side of what then constituted New York City at the southern end of the island of Manhattan .
Simplified: The Great Fire of New York was a large fire that burned through the night of 21 September 1776 on the west side of the former boundaries of New York City at the southern end of the island of Manhattan .