Kilgraston's earliest records date back to the 13th century where it was called Gilgryston. John Grant, the eldest son of Patrick Grant of Glenlochy, in Strath Spey, Inverness-shire, and whose principal wealth was made in Jamaica, was for several years a member of the Assembly there, becoming an assistant Judge of Jamaica's Supreme Court, and eventually succeeded Thomas French as Chief Justice of that island in January 1783, which office he held until 1790. Also, in 1783, he was confirmed as an armiger by the Lord Lyon King of Arms. Grant purchased, towards the end of the 18th century, from the Murray and Craigie families, the contiguous estates of Kilgraston and Pitcaithly, situated in the east end of the beautiful and rich valley of Strath Earn, and extending over part of the Ochil Hills. He died issueless at Edinburgh on 29 March 1793, and is buried under a marble tablet in St Cuthbert's Churchyard. He was succeeded in his estates by his brother Francis (d. 1819, who built the mansion. The mansion was used as a private home until World War I during which it was used as a hospital.