Complex sentence: In 1851 Annin made flags for Queen Victoria of Great Britain for the Queen's "Great Exhibit of the Works of Industry of All Nations" in London, considered by historians to be the first World's Fair.
Split into simpler sentences: In 1851 Annin made flags for Queen Victoria of Great Britain for the Queen's "Great Exhibit of the Works of Industry of All Nations" in London. This event is considered by historians to be the first World's Fair.