The county council was established in 1889 as the principal local authority for the historic county of Wiltshire. It continued as such until April 1997, when the borough of Swindon became a unitary authority, taking almost a third of the population out of the area then falling under Wiltshire County Council. From 2009, it became Wiltshire Council.
4 May 1989: Conservatives 35, Liberal Democrats 18, Labour 18, Independents 2, Liberal 1, SDP 1, resulting in a continuation of no overall control, this time with the Liberal Democrats and Labour forming a joint administration.
6 May 1993: Liberal Democrats 33, Conservatives 18, Labour 17, resulting in a further four years of no overall control, with a Liberal Democrat and Labour administration.
On 1 April 1997, Swindon was separated from Wiltshire to become a new unitary authority, giving the Liberal Democrats a brief period of overall control before that year's election.
1 May 1997 (the same day as the general election of 1997): Conservatives 22, Liberal Democrats 20, Labour 4, Independent 1, resulting in a continuation of no overall control, with a new Liberal Democrat and Labour administration being formed.
On 2 April 1998 the Conservatives won a by-election in the Whorwellsdown division by 17 votes, and at the annual meeting in May 1998 a Conservative and Independent administration was formed.
On 13 January 2000, the Conservatives won another by-election, this time in Melksham Without, gaining an overall majority which they were able to hold until the following year's elections.
7 June 2001 (a later date than usual to coincide with the general election of 2001): Conservatives 28, Liberal Democrats 14, Labour 3, Independents 2.
5 May 2005 (again coinciding with a general election): Conservatives 28, Liberal Democrats 16, Labour 3, Independents 2. Wiltshire County Council came to an end on 1 April 2009, when a new Wiltshire Councilunitary authority was formed.