William St. Clair of Roslyn was made a Free and Accepted Mason May 7th 1736.
He was the grand son of the William St. Clair, a purported Knight Templar, who financed and planned the construction, in 1484, of the famous Roslyn Chapel.
On June 2nd 1736 he was raised to the degree of Master Mason. He was then elected First Grand Master of the newly formed Grand Lodge of Scotland on the 30th of December 1736.
Most Worshipful William St. Clair died in 1778 at the age of 78 and was buried at Roslyn Chapel. There were over 400 members of Scottish Masonic Lodges present at his funeral.