The DUP was founded in 1971 by Ian Paisley and Desmond Boal. It was the successor to the Protestant Unionist Party which had been to the fore in the late 60's in opposing the tentative reforms of Terence O'Neill.
The DUP backed the 1974 Ulster Workers' Strike that brought down the pwoer sharing executive spawned by the Sunningdale Agreement.
And it supported also the less successful 1977 Loyalist Strike called to demand tougher security policies against republicanism.
In the mid 80s it then joined with mainstream official Unionists in opposing the Anglo Irish Agreement.
Initially it was hostile to the peace process (including the December 1993 Downing Street Declaration) and the Good Friday Agreement. However in 2007 it agreed to share power at Stormont with Sinn Fein (which led in turn to critics founding Traditional Unionist Voice).
The DUP is now led by Arlene Foster MLA and draws its support both from the Protestant urban working class in the six counties and, through the Free Presbyterian Church of Ulster, from rural evangelicals.