By the sixtennth century Wales had long been an important part of the English realm, but it was left under a mediæval system of marcher lords and unreformed local laws inherited from the plethora of former Welsh states. Wales was given equal status (and representation in Parliament) under King Henry VIII (of the Welsh House of Tudor). In 1535 Wales was made part of England. The marcher lordships were abolished and English law was extended to Wales.
For the text of the Acts effecting the union I am grateful to Owain Vaughan:
Laws in Wales Act 1535 (also
called "the Act of Union 1542")
The Laws in Wales Act 1542
In 1706, commissioners appointed on behalf of Scotland and on behalf of England met to negotiate the terms of a union between the two kingdoms. Agreement was reached swifty and a Treaty of Union, with twenty-five Articles, was concluded on the 22nd July 1706. The Union took effect "on the first Day of May which shall be in the Year one thousand seven hundred and seven".
The Treaty was enacted by twin Acts of the Parliaments of Scotland and then of England. The Parliament of Scotland made some amendments and clarifications before approving the Articles. The English Parliament passed the amended version. The full text of the Treaty was set out in the Acts.
The two Acts were given short titles retrospectively in the nineteenth centuries for ease of reference: "The Union with England Act 1707" and "The Union with Scotland Act 1706". (The 1707 Act was passed before the 1706 Act; the dating is because the English legal year began on 25 March. Not until 1752 did England and the rest of the British Empire catch up with Scotland and have the year beginning on 1st January.)
The English Act is the more comprehensive, incorporating the Articles of Union and the text of two Scottish Acts, on the manner of electing Peers and Members and on the securing of the Kirk. I have given the original text of both Acts in full as they appear in the statute books.
The Union with England Act 1707 - full original text
The Union with Scotland Act 1706 - full original text
The Union with England Act in current form as amended on the Statute Law Database
The Union with Scotland Act in current form as amended on the Statute Law Database
Ninety-three years later the union was complete, with the further union between Great Britain and Ireland: click here for original text.
The Union was the final, crowning act of the Settlement following the Glorious Revolution of 1688. The Revolution Settlement made it possible. I have included a separate page on the Glorious Revolution and the fundamental documents of the settlement, the Bill of Rights and the Claim of Right.
For those documents, go to "Settlement"
The uniting of Great Britain was the greatest step in the creating of the kingdom. However Ireland remained a separate kingdom, dependent on and subordinate to Great Britain. Great Britain and Ireland were united only on 1st January 1801, by the Acts of Union 1800.
For the documents of that Union, go to "The Acts of Union 1800".