Institutional reform in mental healthcare started in the eighteenth century with the construction of a small number of facilities in Dublin and Cork specifically for the treatment of mental illness. The 1800s witnessed the construction of an extensive network of district lunatic asylums in two phases: pre-Famine and post-Famine. The last major construction occurred in Portrane, County Dublin at the end of the nineteenth century. The Ardee Mental Hospital, County Louth, opened in November 1933. It was the only mental health facility constructed in the Irish Free State period. Until this time, patients from County Louth were accommodated in the Richmond District Lunatic Asylum in Dublin. This thesis argued that the Local Government (Ireland) Act (1898) reinvented the political, economic and moral justifications for institutional reform in mental healthcare and produced a new generation of mental health reformers in County Louth. The efforts of members of Louth County Council and subsidiary councils in the first decades of the twentieth century led, firstly, to official separation between the council and the Richmond asylum authorities in 1930 and, secondly, to the construction of a purpose built mental hospital on part of the Ruxton estate in Ardee. The Ardee Mental Hospital was an icon of modern mental healthcare in twentieth-century Ireland which was examined in this research through a number of historical contexts: politics (local government in County Louth), economics (the economics of institutional mental health care), the unionisation of nurses in Irish mental hospitals (labour history), the professionalisation of staff and advances made in the treatment of mental illnesses (the rhetoric of mental healthcare in twentieth-century Ireland).