The first Royal Union Flag sometimes called the Queen Anne Flag was created by command of James I of England (formerly James VI of Scotland) and it symbolized the union of those two countries. It is composed of the Cross of St. George (a red cross on a white background) and the Cross of St. Andrew (a diagonal white cross on a blue background). By 1707 it was known as the Union Jack and accepted as the flag of the British Empire. It was the flag of Canada from 1759 to 1801 and the flag the Loyalists carried on their migration.
Reference: Branch President's Manual, UELAC; Flag image provided by Bill Smy.