The estate was established by John Adair, who became infamous for evicting 244 of his tenants and clearing the land so they would not spoil his view of the landscape. The gardens and castle were presented to the Irish nation in 1981 by Henry P. McIlhenny of Philadelphia who had purchased the estate in 1937. The castle was built by Captain JohnGeorge Adair, a native of County Laois, and a member of the minor gentry. Adair had made his fortune in the United States, and he returned to Ireland and bought up vast tracts of land in Donegal. Adair had married in 1869, Cornelia Wadsworth Ritchie, a daughter of James S. Wadsworth, a Union General in the American Civil War. Together they set about the creation of the gardens and castle. Adair's ambition was to create an estate and castle that surpassed Balmoral, Queen Victoria's Scottish retreat. His troubles with Irish tenants on his land began immediately. A row between them and Adair over shooting rights and trespassing sheep culminated in the murder of Adair's Scottish steward James Murrog. Consequently, John Adair evicted 44 families from their blackhouses on his land. His widow Cornelia Adair took over ownership of the castle and estate after John Adair's death in 1885. She lived part-time at Glenveagh Castle, and improved the beauty of the castle grounds. She brought much biodiversity with both practical and exotic ambitions. Practical being Fast Growing and long living Pines that would offer wind shelter to the castle and gardens. The pines along the river and lake also helped prevent the flooding of the grounds and along the banks. The pleasure grounds were created as a garden oasis that would showcase exotic and native plants, trees, and flowers from around the world. The Rhododendron was brought in as an ornamental as well as practical solution for wind breaking and protection. Mrs Adair's long Rhododendron hedge had grown into a tall wall that followed the drive up to the castle. This was a wonderful wind shelter and introduction to coming up to the castle. December 2018, this historical hedge was destroyed entirely to put in a new water pipe. Henry Plumer McIlhenny of Philadelphia, USA purchased the estate in 1937. McIlhenny left the gardens and castle to the Irish nation in the 1970s, but continued to use the castle as a part-time residence until 1982.
Environment
The park is home to the largest herd of red deer in Ireland and the formerly extirpatedgolden eagle were reintroduced into the park in 2000. There is no park ranger in Glenveagh National Park. All decisions are made by administration that is an extension of the department of environment of the Irish Government. In winter 2018 and spring 2019, many native and non-native trees and plants were cleared from the park, and the water and pipe system was updated. 2019 increased Deer Tick population reported.
