The Union of Great Britain and Ireland was formed on January 1, 1801, when the Kingdom of Great Britain and the Kingdom of Ireland merged into a single political entity. This union created the United Kingdom of Great Britain and Ireland, which aimed to strengthen political and economic ties between the two regions. The union lasted until 1922, when most of Ireland left to become the Irish Free State. This change led to the establishment of the United Kingdom of Great Britain and Northern Ireland, which includes Northern Ireland and continues to exist today.