The history of the United Kingdom as a unified sovereign state began with the political union of the kingdoms of England, which included Wales, and Scotland on 1 May 1707 in accordance with the Treaty of Union, signed on 22 July 1706,[1] and ratified by both the Parliaments of England and Scotland each passing an Act of Union. The Union created the United Kingdom of Great Britain,[2] which shared a single constitutional monarch and a single parliament at Westminster. Prior to this, the kingdoms of England and Scotland had been separate states, though in personal union following the Union of the Crowns in 1603, with political, administrative and cultural institutions including representative governance, law systems, and distinguished contributions to the arts and sciences, upon which the United Kingdom was to be built. On the new, united kingdom, historian Simon Schama said "What began as a hostile merger would end in a full partnership in the most powerful going concern in the world... it was one of the most astonishing transformations in European history."[3] A further Act of Union in 1800 added the Kingdom of Ireland to create the United Kingdom of Great Britain and Ireland.