||Peter McSweeney was leasing the property at Derreen from the Lansdowne estate at the time of Griffith's Valuation, when it was valued at £6 10s. Lewis also notes it as his residence in 1837. Bary states that Derreen was originally built by a branch of the O'Sullivans from whom it passed to Peter McSweeney who was married to a member of that family. It formed part of the Lansdowne estate and later came into the possession of the Petty-Fitzmaurices. In 1906 it was owned by that estate and was valued at £53 15. It was burnt in the early 1920s but rebuilt in the same style and is still extant and occupied. It is famous for its beautiful gardens.