This thesis examines the political development o f County Mayo during the years 1780- 1830, through the lens o f its leading political dynasty, the Browne family o f Westport. The two central characters are John Denis Browne (1756-1809), third Lord Altamont and first marquess o f Sligo, and his brother Denis Browne (1763-1828), long serving MP for the county and leading magistrate. By unlocking the personal and political history o f the Brownes, the most economically powerful and politically influential family in the region, it is possible to identify and examine changing patterns o f governance in Ireland. The public lives o f the Brownes coincided with a gradual shift away from the patrician and paternalistic model o f local governance towards a more centralised pattern emanating from Dublin and London. Their political biographies cover pivotal stages in Irish history during the late eighteenth and early nineteenth centuries; the ongoing Catholic question, the suppression o f radicalism in the 1790s, the Union and manifestations o f agrarian insurgency and poor relief. Throughout this period, the Brownes were in constant contact with senior officials in Dublin and this, often tense, relationship revealed a growing divergence between the ruling elite o f Mayo and official government policy. The appointment o f Robert Peel as C hief Secretary in 1813 intensified this divergence as the maintenance o f law and order, for centuries the reserve o f local gentry figures, was brought further under the direct control o f Dublin. As county Mayo moved from being a domain, controlled by a hand full o f powerful families (the Brownes, Binghams, Cuffes, Dillons), to a more accessible and provincial part o f the wider United Kingdom, the Brownes’ political ambitions began to gradually recede, their political hegemony and influence eventually being replaced by the state and an emerging Catholic bourgeoisie in the wake o f Emancipation.