King David I invited Norman knights to take up lands in Scotland in the 12th century. Among those knights were the Hunters, who settled in North Ayrshire. For hunting services to David I, Aylmer was made Hunter Royal in 1160 (a hereditary title which has been passed down for over 900 years) and in 1271 Alexander III gave the Hunters a charter for additional lands in North Ayrshire.
The pele tower was originally built in the 13th century at the behest of King Alexander III, who urged his vassals to build towers to defend against raiding Norsemen. The area surrounding the castle was initially a dangerous swamp (the castle even had a moat and rampart). However, this swampland was eventually drained to make way for pasture land.
The tower was raised in the 15th century before the castle was rebuilt and added to in the following centuries, with Hunterston House being added in the 17th century.
An interesting occupant of Hunterston Castle was the famous First World War general, Aylmer Hunter-Weston (1864 – 1940). Aylmer was the first-born son of Lieutenant-Colonel Gould Read Weston and his second wife Jane Caldwell Hunter – the eldest daughter of the 25th Laird of Hunterston. On the morning of March 18th he fell from the 45 foot tower and died. He was 75 years old.