Plas Newydd is a country house set in gardens, parkland and surrounding woodland on the north bank of the Menai Strait, in Llanddaniel Fab, near Llanfairpwllgwyngyll, Anglesey.
The land was first occupied in the 13th century, known as Llwyn-y-Moel. By 1470 it belonged to the Griffith family, who also owned Penrhyn Castle near Bangor. Gwilym ap Griffith inherited the land from his marriage to Morfydd, daughter of Goronwy ap Tudur of Penmynydd. It was Robert Griffith who built the earliest parts of the current house in the early 16th century.
Lewis Bayly, related to the Griffith family by marriage, made the first major additions to the house, calling it Plas Newydd, New Hall. The Baylys lived in Plas Newydd, along with other estates, particularly in Ireland, and Lewis's grandson Edward Bayly acquired an Irish baronetcy in 1730. Lewis's great-grandson Sir Nicholas Bayly, 2nd Baronet, became Lord Lieutenant of Anglesey in 1761, a position his family would fill for the next 100 years.
Born in 1744 as Henry Bayly, he succeeded, through his mother, to the title and estates of the Barony of Paget in 1769, on the death of Henry Paget, 8th Baron Paget and Earl of Uxbridge, a distant cousin on his mother's side. Under Henry's care there were substantial additions and rebuilding throughout the estate, especially with the appointment of James Wyatt and Joseph Potter as architects.
James Wyatt, re-faced the building, blended the towers into the building front, making it into the building that stands today. He also had constructed the large Gothic style stable block which is now part of the Conway Centre, as well as various lodges and gateways.
In 1812 Henry died, and the estate passed to his son Henry William Paget, who became the 2nd Earl of Uxbridge. Henry William had raised a regiment of volunteers in the 1790s, was commissioned into the Army in 1795, distinguishing himself in numerous engagements and campaigns across Europe. By 1802 he was a major-general, then in 1815 was appointed cavalry commander, leading a spectacular charge of the British heavy cavalry at the Battle of Waterloo. In recognition of his heroism he was created the first Marquess of Anglesey, although he lost a leg from one of the last cannon shots of the day. The following year the 27 metre column was raised in his honour, sited to the north of Plas Newydd.
At the end of the 19th century the 5th Marquess inherited the family seat, which he renamed Anglesey Castle. Renowned for his lavish spending and flamboyant lifestyle, he converted the family chapel inside the house into the Gaiety Theatre. Plays were put on regularly, with 'the Dancing Marquess' often taking the lead role himself.
The 5th Marquess's extravagant spending drained the family fortune, and after his death in 1905, 6th Marquess began to sell off assets to help restore the solvency of the family. The family also sold off their main home at Beaudesert and their London house, and moved into Plas Newydd permanently. The 6th Marquess made the final big changes to the house by removing the crenellations from the roof, disposing of the theatre, knocking three servants' rooms together to make the dining room and covering over a courtyard to provide a roof for the servants.
There are two prehistoric scheduled monuments on the site but they are not accessible to the public, although they can both be seen. The two monuments formed a single entry in the first Ancient Monuments Act in 1882. Plas Newydd Burial Chambers are two adjoining stone chambers of a Neolithic burial cairn or cromlech. They stand on private lawns in front of the house.
Bryn-yr-Hen-Bobl Burial Chamber Hill of the old people, is a substantial mound with a stone chamber to the south of the parkland. Bones were found in 1754. It was excavated by W J Hemp in 1929–35, Neolithic pottery appeared to lie under and in front of the mound, suggesting a settlement predating its use as a burial site. The chamber was given a doorway following the dig. It is visible from the southern edge of Garden Wood.
The house and grounds, with views over the strait and Snowdonia, are open to the public, having been owned by the National Trust since 1976.