The Union Jack is a composite of three crosses: St. George’s, St. Andrew’s, and St. Patrick’s. The first Union flag, the St. George’s Cross over the St. Andrew’s Cross, was introduced for ships in 1606. In 1660, the British flag was officially described as the Union Jack. St. Patrick’s Cross was added in 1801. In 1933, it was decreed that the Union Jack could be flown on land by any British subject.
Overseas Territories and Crown Dependencies of the United Kingdom