John Hamilton, (1800-1884), a wealthy and philanthropic landlord, owned large estates at Brownhall in south Donegal. In 1824, Hamilton decided to build a small dwelling on St. Ernan's Island in Donegal Bay, and in due course, with the help of the local tenantry, and with great difficulty, he built a causeway over to the island. Hamilton was a good landlord, and was liked and respected by all creeds and classes. He liked St. Ernan's so much, that he soon decided to build a much larger house there.
Over the years, this house was sold a number of times to different buyers, until it became into the procession of the Dane-Morgan family. In the early 1950s, they bequeathed St. Ernan's to the Church of Ireland. Thus, it became a holiday home for clergy families. It remained as such until closure in the mid-1970s. It is now a hotel.