Blackness Castle is a 15th century fortress, near the village of Blackness, Scotland, on the south shore of the Firth of Forth. It was built, probably on the site of an earlier fort, by Sir George Crichton in the 1440s. At this time, Blackness was the main port serving the Royal Burgh of Linlithgow, one of the main residences of the Scottish monarch. The castle, together with the Crichton lands, passed to King James II of Scotland in 1453, and the castle has been crown property ever since. It served as a state prison, holding such prisoners as Cardinal Beaton, and the 6th Earl of Angus.