Complex sentence: Also arriving to this area in substantial numbers around 1787 were the United Empire Loyalists still loyal to the British crown fleeing from the United States after the 1776 American War of Independence.
Split into simpler sentences: Also arriving to this region afterwards but in greater numbers around 1787 were the United Empire Loyalists that were still loyal to the British crown. These loyalists were fleeing from the United States after the 1776 American War of Independence.