The two countries had shared a monarch for about 100 years (since the Union of the Crowns in 1603, when King James VI of Scotland inherited the English throne from his cousin, Queen Elizabeth I). Although described as a Union of Crowns, until 1707 there were in fact two separate Crowns resting on the same head. There had been three attempts in 1606, 1667, and 1689 to unite the two countries by Acts of Parliament, but it was not until the early 18th century that the idea had the will of both political establishments behind them, albeit for rather different reasons.
The Acts took effect on 1 May 1707. On this date, the Scots Parliament and the English Parliament united to form the Parliament of Great Britain, based in the Palace of Westminster in London, the home of the English Parliament. Hence, the Acts are referred to as the Union of the Parliaments. There was an attempt to rename Scotland and England as North and South Britain. This was generally short lived, particularly in "South Britain" - although the name "North Britain" lingered for a while in some institutions. This practice is now rarely, if ever, seen.
On the Acts of Union, 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.
Later in the seventeenth century the Estates of Scotland petitioned a number of times for a union but were rejected by England.
The Solemn League and Covenant sought a forced union of the Church of England into the Church of Scotland, and although the covenant referred repeatedly to union between the three kingdoms, a political union was not spelled out. In the aftermath of the Civil War, in which the Covenanters had fought for the King, Oliver Cromwell conquered Scotland and by force created the Commonwealth of England, Scotland and Ireland, a brief union which was dissolved by the restoration of King Charles II. Scottish members expelled from Parliament petitioned unsuccessfully for a continuance of the union.
At the Glorious Revolution in 1689, the records of the Scottish Parliament show much discussion of possible union. Nothing was done. Thereafter relations between the English and the Scots deteriorated, largely perhaps through the English stranglehold on Scottish trade and ultimately because of the failure of the Darien Scheme and the popular perception in Scotland that the scheme's failure was the fault of the English.
The ultimate securing of the treaty in the unicameral Scottish Parliament is sometimes attributed to the weakness and lack of cohesion between the various opposition groups in the House, rather than to the strength of pro-incorporationists. The combined votes of the Court party with a majority of the Squadrone Volante were sufficient to ensure the final passage of the treaty through the House.
Personal financial interests were also involved. Many Commissioners had invested heavily in the Darien Scheme and they believed that they would receive compensation for their losses; Article 14, the Equivalent granted £398,085 10s sterling to Scotland to offset future liability towards the English national debt. In essence, it was also used as a means of compensation for investors in the Darien Scheme.
Even more direct bribery was said to be a factor. £20,000 (£240,000 Scots) was dispatched to Scotland for distribution by the Earl of Glasgow. James Douglas, 2nd Duke of Queensberry, the Queen's Commissioner in Parliament, received £12,325, the majority of the funding. (Other studies suggest that all of this money was properly accounted for as compensation for loss of office, pensions and so forth not outwith the usual run of government. It is perhaps a debate that will never be set to rest.) Robert Burns referred to this:
Some of the money was used to hire spies, such as Daniel Defoe; his first reports were of vivid descriptions of violent demonstrations against the Union. "A Scots rabble is the worst of its kind," he reported, "for every Scot in favour there is 99 against". Years later John Clerk of Penicuik, originally a leading Unionist, wrote in his memoirs that,
Defoe recalls that he was hired by Robert Harley.
The Treaty was not universally popular in Scotland. Many petitions were sent to the Scottish Parliament against Union, and there were massive protests in Edinburgh and several other Scottish burghs on the day it was passed , as threats of widespread civil unrest resulted in the imposition of martial law by the Parliament. Sir George Lockhart of Carnwath, a Jacobite and the only member of the Scottish negotiating team who was not pro-incorporation, noted that `The whole nation appears against the Union'. Sir John Clerk of Penicuik, an ardent pro-unionist and Union negotiator, observed that the treaty was `contrary to the inclinations of at least three-fourths of the Kingdom'.
Public opinion against the Treaty as it passed through the Scottish Parliament was voiced through petitions from Scottish localities. Anti-union petitions were received from shires, burghs, presbyteries and parishes. The Convention of Royal Burghs also petitioned against the Union and not one petition in favour of an incorporating union was received by Parliament. On the day the treaty was signed, the carilloner in St Giles Cathedral, Edinburgh, rang the bells in the tune Why should I be so sad on my wedding day?
Ireland's benefits from the Union of 1707 were few. Its preferential status in trade with England now extended to Scotland. The strengthening of Great Britain improved Ireland's defence against enemies, whether foreign or domestic. Nevertheless, Ireland was left unequal and unrepresented in the Parliament of Great Britain.
In July 1707 each House of the Parliament of Ireland passed a congratulatory address to Queen Anne, praying that "May God put it in your royal heart to add greater strength and lustre to your crown, by a still more comprehensive Union. The British government did not respond to the invitation and an equal union between Great Britain and Ireland was out of consideration until the 1790s. The union with Ireland finally came about on 1 January 1801.
The two Acts incorporated provisions for Scotland to send representative peers from the Peerage of Scotland to sit in the House of Lords. It guaranteed that the Church of Scotland would remain the established church in Scotland, that the Court of Session would "remain in all time coming within Scotland", and that Scots law would "remain in the same force as before". Other provisions included the restatement of the Act of Settlement 1701 and the ban on Roman Catholics from taking the throne. It also created a customs union and monetary union.
The Act provided that any "laws and statutes" that were "contrary to or inconsistent with the terms" of the Act would "cease and become void."
Soon after the Union, the Act 6 Anne c.40 (later infelicitously named the "Union with Scotland (Amendment) Act 1707") united the English and Scottish Privy Councils and decentralised Scottish administration by appointing justices of the peace in each shire to carry out administration. In effect it took the day to day government of Scotland out of the hands of politicians and into those of the College of Justice.
Defoe drew upon his Scottish experience to write his Tour thro' the whole Island of Great Britain, published in 1726, where he actually admitted that the increase of trade and population in Scotland, which he had predicted as a consequence of the Union, was "not the case, but rather the contrary."
Andrew Fletcher of Saltoun, a vehement critic of the Union, said in An Account of a Conversation, that Scotland suffered "...the miserable and languishing condition of all places that depend upon a remote seat of government."
However by the time Samuel Johnson and James Boswell made their tour in 1773, recorded in A Journey to the Western Islands of Scotland Johnson noted that Scotland was: “a nation of which the commerce is hourly extending, and the wealth encreasing”, and Glasgow in particular had become one of the greatest cities of Britain.
In his position as Speaker in 1713, William Bromley responded to questions from a Scottish MP with the reply that "they had catcht hold of Scotland, they wou'd keep her fast". Lockhart Papers Page 427
The Lord Treasurer Robert Harley, 1st Earl of Oxford and Earl Mortimer (Circa 1712) when debating increasing taxes on linen stated "Have we not bought the Scots, and a right to tax them?" Lockhart Papers Page 327
"In Edinburgh and Glasgow there were open riots." 
"In Dumfries The Treaty was openly burned." 
"It was opposed by the majority of the Scottish people." 
"The Scottish members of the united parliament felt their insignificance, and were too evidently despised by their English brethren."
"Their united opposition was utterly lost in the multitude of their opponents."
"The English majority, and not the Scottish members, legislated for Scotland."
A commemorative two-pound coin was issued to mark the 300th anniversary of the Union, which occurred two days before the Scottish Parliament general election on 3 May 2007.
The Scottish Government announced plans for a year-long commemoration including an education project led by the Royal Commission on the Ancient and Historical Monuments of Scotland, an exhibition of Union-related objects and documents at the National Museums of Scotland and an exhibition of portraits of people associated with the Union at the National Galleries of Scotland.