 The estate was bought by James Graham, 3rd Marquess of Montrose (1657–1684), whose son became the 1st Duke of Montrose in 1707.The Montrose family occupied the existing Buchanan Auld House and this eventually replaced Mugdock Castle as the seat of Clan Graham, being seen as a dwelling more fitting the title of "Marquess".The original house was substantially rebuilt from approximately 1724.