It began to take its present shape with the Acts of Union in 1707 , which united the crowns and Parliaments of England and Scotland to create the Kingdom of Great Britain .
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 , as ratified by the Acts of Union 1707 . The Union created the Kingdom of Great Britain , which shared a single constitutional monarch and a single Parliament of Great Britain at Westminster .