Wicklow Mountains National Park was established by the government in 1991 with an initial core area of 3,700 ha (37 square km). This core area comprised the statutory nature reserves of the Glendalough Woods and the adjacent Glenealo Valley, both of which were established in 1988. Lands were also transferred from the state's commercial timber production agency, now known as Coillte Teoranta. These plots of land amounted to more than 2,900 ha (29 square km). They were no longer required for planting purposes but were of high conservation value. Lands around the Liffey Head Bog complex were also purchased from the Powerscourt Estate at that time.
Since then, further lands have been transferred by Coillte Teoranta for inclusion in the Park. Purchase of land from private landowners has also continued when the land is put on the market for sale. No land has been acquired through compulsory purchase. The main areas purchased were in Ballingonneen, Kippure East, Ballinabrocky, Lough Bray, Derrybawn, Glencree and Ballinastoe. This piecemeal acquisition has resulted in a patchwork of Park lands. The boundaries of the Park as it exists at present, are based on previous land ownership patterns, rather than on an ecological unit. Currently the Park is approximately 20,000 ha (200 square km) in area but will continue to grow as new lands are acquired.
Much of the lands within the site are commonage (areas over which traditional communal land-use rights exist). These rights include grazing, turbary (turf collection) and estovers (e.g. wood collection). These rights are recognised and a liaison process with rights holders has been established to achieve the conservation objectives of the Park.
Responsibility for the Park has passed between a number of government departments over the years and currently rests with the Minister of the Arts, Heritage and the Gaeltacht, through the National Parks and Wildlife Service.