Built in the 1370s by Archibald the Grim, it was a stronghold of the "Black Douglases", Earls of Douglas and Lords of Galloway, until their fall in 1455. For part of this time, the castle and the lordship of Galloway were controlled by Princess Margaret, daughter of King Robert III and widow of the 4th Earl. In 1449 Threave was regained by the 8th earl, Scotland's most powerful magnate, who controlled extensive lands and numerous castles. He fortified Threave with an "artillery house", a sophisticated defence for its time. The excessive power of the Black Douglas lords led to their overthrow by King James II in 1455, after which Threave was besieged and captured by the King's men.