Two great-grandsons of Arthur Guinness, Arthur and Benjamin Lee Guinness built up a large estate in the Clontarf/Raheny area from 1835 onwards.
They called it St. Anne's after the holy well that sat on the site. Of the two brothers, Sir Arthur Edward Guinness (Lord Ardilaun) was primarily responsible for the expansion and development of the estate and gardens.
Lord and Lady Ardilaun had no children, so the estate passed to their nephew Bishop Plunkett in the 1920s. In 1937, he decided he could no longer maintain such a large estate. He sold it to Dublin Corporation for approximately £55,000 in 1939, retaining Sybil Hill (now St. Paul's College) and 30 acres of parkland as a private residence.
Just over 200 acres of the estate were developed for public housing while the central 270 acres were retained as parkland.
In December 1943, the main residence of St. Anne's "The Mansion" was gutted by a fire. The ruins were demolished in 1968. The Tudor “Red Stables” survived.
To celebrate Dublin’s Millennium in 1988, the Parks Department in co-operation with the Tree Council of Ireland, created the Millennium Arboretum. The arboretum is planted with over 1000 types of trees, sponsored by 1000 participants.