The constituency consisted of the whole county of Durham. Because of its semi-autonomous status as a county palatine, Durham had not been represented in Parliament during the medieval period; by the 17th century it was the only part of England which elected no MPs. In 1621, Parliament passed a bill to enfranchise the county, but James I refused it the royal assent, as he considered that the House of Commons already had too many members and that some decayed boroughs should be abolished first; a similar bill in 1624 failed to pass the House of Lords. During the Commonwealth, County Durham was allowed to send members to the First and SecondParliaments of the Protectorate, though the privilege was not maintained when Parliament reverted to its earlier electoral arrangements from 1658. After the Restoration, Durham's right to return MPs was recognised in 1661, and finally confirmed by statute which came into effect in 1675; the county was to return two members, and the same Act also established Durham City as a parliamentary borough with its own two members. As in other county constituenciesthe franchise between 1430 and 1832 was defined by the Forty Shilling Freeholder Act, which gave the right to vote to every man who possessed freehold property within the county valued at £2 or more per year for the purposes of land tax; it was not necessary for the freeholder to occupy his land, nor even in later years to be resident in the county at all. By the time of the Reform Act, the county had a population of just over 250,000, although this was slightly reduced by the boundary changes which severed the enclaves and made them part of Northumberland or the North Riding of Yorkshire for parliamentary purposes. The electorate was only a fraction of this number: at the general election of 1790, 5,578 voted, and in 1820 the number was only 3,741. Although nobody could exert the degree of control over the voters that was common in many boroughs, several of the major local landowners had significant influence, in particular the Vane Earls of Darlington. In 1832 the county's representation was doubled, and the constituency divided into two new two-member constituencies, North Durham and South Durham.
